/sci/ - Science & Math

Why is this marked bond a R-configuration?
Shouldn't it be a S configuration by the Chloride next to it?
Has it to do with it being in the background (the strange wedges indicate it is in the background)?

>>9855720
Assign priorities:

1. Cl
2. CHCl (counter clockwise around ring)
3. CHC (clockwise around ring)
4. H (not illustrated)

Note that H must be projecting out of the plane of the page.

Rotate so that H is projecting into the plane of the page. Absolute configuration can only be assigned when the lowest priority group is facing away from the viewer.

Trace a line from priority groups 1 -> 2 -> 3 and note it's clockwise. Therefore absolute configuration is R.

Alternatively: Ignore H's location, don't flip the molecule, and simply trace 1 -> 2 -> 3. Now we're moving counterclockwise. However, H is facing forward, so we need to reverse the configuration. Counterclockwise indicates S, which reverses to R.

Alternatively 2: Swap the positions of H and Cl on the stereogenic carbon. Swapping the positions of any 2 substituents on a stereogenic carbon reverses the absolute configuration. Now you can trace 1 -> 2 -> 3, and since H is at the back, this is an S configuration (it traces counterclockwise). However, when you swapped H and Cl, you reversed the absolute configuration. Reversing the 'real' configuration gave you S, so the real config must be R.

>>9855744
Ok, totally forgot that I can turn the molecule in my head.
Now it makes sense,

Brainlet here. This video seems to make sense to me. Why is it wrong? It's just 37 seconds.

https://youtu.be/AibJiMq62p0

These threads are shit. You guys take the concept of “stupid questions” and just go overboard with it. Go ask your asinine inquiries on ELI5.

I'm stumped on what kind of statistic test to use for one segment of my paper. It's related to microbiology where I'm evaluating Minimal Inhibitory Concentration (MIC) of different things (X, Y, Z) solo (MICs) and in mixture (MICm) with each other in three different concentration mixtures (for example, in mixture 1 I have 200 ppm of X, 10 ppm of Y, 50 ppm of Z, while in mixture 2 some other values). I did experimental part long ago and got MICs of X, Y, Z and I got MICm for mixtures 1, 2, 3. I calculate MICm of X, Y, Z by multiplying the amount of X, Y, Z and the MICm of mixtures 1, 2, 3. For example, if mixture 1 has MICm of 12.5% (0.125) and it has 200 ppm of X, then MICm(X1)=200 ppm * 0.125=25 ppm.

In order to determine existence of synergism, I have to calculate something called Fractionary Inhibitory Concentration Index (FICI). Basically, for any single mixture of X and Y and Z, I divide MICm(X) with MICs(X), do the same with Y and Z, then add all these things together. The problem is that both MICm(X) (the MIC of X in mixture) and MICs(X) (the MIC of X solo) are experimentally determined values with their own mean and st.deviation. So I have no idea what statistic test to use to determine if there is difference between three different mixtures.

Already went through the sum of squares leading up to n proof from Apostol's calc book
1^2 + 2^2 + ... + n^2 = (n^3)/3 + (n^2)/2 + n/6
but I don't get how they made the jump for this formula to pic related inequality?
Note the typing error on (n-1)", should be (n-1)^2

>>9855388
So, went through 6 chapters of this book, seems sketchy and all over the place. But let's say I have down the basic topics of factorizations, eigenvalues, determinants. The section on linear transformations lost me. What book would you recommend for more organized approach with more depth and emphasis on theory, possibly going quickier through the topics I have already gone through?

If the moon is spherical, why is all of it lit up equally during a full moon?

>>9856514
It's not, only half of it
the light difference within the lit area is just so small you can't tell

>>9856515
Why does the part of the moon in "shadow" not show up in a thermal imaging camera?

>>9856360
>These threads are shit. You guys take the concept of “stupid questions” and just go overboard with it. Go ask your asinine inquiries on ELI5.
What's your question?

>>9856594
Sun isn't hitting it so it's not hot
Socho bhenchod

>>9856594
I reckon it's cold innit

>>9856480
axler's linear algebra done right is the go to

>>9856470
the second equality is obvious from the formula, since the other two terms are strictly positive

the first equality follows from a simple induction arguement

In order to be more productive, what do you thing of a voice recorder during lecture ? Is it worth it ? Do you have any suggestions ?

They're not quite widespread in my country, don't know what it would look like

>>9856642
>>9856651
Why does taking an infrared picture of a solar eclipse reveal the atmosphere around it taking the shape similar to that of earth's magnetic field?

>>9856676
Doubt it's related to earth's magnetic field
Don't actually know why it makes that shape though, probably something to do with earth's curvature? Wild guess, honestly no idea

>>9856676
Because the atmosphere around the sun is made of charged plasma which is following the Sun's magnetic field.

Q. Why does gold come in lumps rather than evenly spread throughout the soil? How do the bits of gold find each other?

>>9856676
>e shape similar to that of earth's magnetic field?

Because the gas is at high temperature and ionized, thus influenced by the Suns magnetic field.

In order to be more productive, what do you thing of a voice recorder during lecture ? Is it worth it ? Do you have any suggestions ?

They're not quite widespread in my country, don't know what it would look like

So I attempted to perform a double replacement reaction [KC4H5O6 + HCl = C4H6O6 + KCl] to yield tartaric acid and potassium chloride from 9.5 ml Cream of Tartar, 10ml muriatic acid, and 100ml of distilled water. Here is what happened:

I measured out 100ml distilled water in beaker. Then I measured out 10 ml of muriatic acid in another beaker. Muriatic acid is diluted HCL with iron impurities which is what gives it a yellow coloration. The concentration of HCL in muriatic acid is anywhere from 20% to 32%. I don't know the exact concentration in the muriatic acid used. I combined muriatic acid into water. Then I measured out 9.5ml of Cream of Tartar and poured it into acidic HCL water. After mixing until everything was dissolved and it was a completely clear solution, I added acetone to solution hoping it would precipitate out KCL salt leaving tartaric acid, water, and acetone in the upper aqueous solution. It didn't precipitate anything. Nothing happened. I assume this is because of an imbalance of HCL and Cream of Tartar. I added a spoonful extra of Cream of Tartar and mixed. It didn't fully dissolve so I added a splash of muriatic acid to solution and mixed. The solution became more milky after stirring. The solution gradually went clear from the top down leaving salts at the bottom. This is due to the acetone. The salts at the bottom COULD be potassium chloride. potassium bitartrate, or a mixture of the two. I decanted the solution into a flat pyrex glass plate leaving salts at the bottom in the beaker. I allowed for the acetone to evaporate overnight. Then next morning, I heated up the remaining solution to 400 F and tried to evaporate the remaining water (which I assume could be acidic). Nothing boiled, but vapors were evaporating off the solution and it gradually lost water. A nasty muriatic acid odor (like pungent mustard) could be smelled and I probably was releasing hydrochloric gas into the air like a dumbass.

continued....

>>9856816
Once nearly all of the solution had evaporated the mustard like smell in my makeshift cardboard fume hood (basically cardboard fort attached to cracked window) made it hard to breathe so I turned off stove and left the cardboard fume hood fort sealing it behind me giving it time to air out. I was only wearing goggles, gloves, long sleeve, and a tee shirt around nose and mouth. After some time had passed small crystals were now on the glass were the solution had evaporated off. What these are is a mystery to me. They could be tartaric acid like I ultimately wanted, they could be potassium bitartrate crystals, they could be HCL crystals for all I know. Interestingly enough I let this pan sit overnight and were the remaining yellow solution was crystals had formed in it too. Whether these crystals are the same as the ones in the pan I am uncertain. I took one out and tried to clean the yellow color off the crystals with acetone and it just completely dissolved instantly. Same with water. The crystals that look yellow in the pic are actually clear and stable at room temperature but are rather fragile. The yellow can come off if patted dry with a paper towel or if it is scraped away. My question is what are these crystals? Are they both the same? I could just buy tartaric acid I know but it is rather difficult to find and not all stores carry it but they do all carry Cream of Tartar. I want to make LSA tartrate using lysergic acid amide saturated acetone that has been basified with sodium carbonate by adding tartaric acid saturated acetone.

Brainlet here, how do I approach this?

How do I ask my research supervisor for a coauthor on the paper we're currently working on without coming across as greedy? Right now I'm just an RA but I feel like I've made enough contribution to the paper to warrant a coauthor

>>9857293
Son, just walk right up to him and firmly shake him right in the eye.

>>9857103
subtract the point from the two lines, then take their cross product to get a vector perpendicular to them (simply set t=1 for that). then times that vector with lambda and add the point to it. done.

>>9857311
>subtract the point from the two lines
Can you elaborate on this and why set t=1 for the cross product?

>>9857103
The lines have directions <-4,7,-3> and <-4,1,-1>. The perpendicular direction is the cross product of those two, which is <-4,8,24> (or divide by 4 to get <-1,2,6>), and you're given that it passes through <6,5,4> at t=0, so <6-t,5+2t,4+6t>.

>>9857296
I hate that faggot so much, quintessential butthurt right winger who takes out his resentment for hard labor by trying to force it on everyone else. Once based Elon and Bezos hail in the gibs paradise of demand side economics then he can finally get the rope.

How do I stop struggle over simpliest tasks? I am doing course on series at the moment, face problems heavily. I can't concentrate on longer than two minutes.

How do I make through it? What do you feel when you start learning something unknown? At what rate?

>be me
>get bullied by this girl and her friends
>hold the grudge for years
>girl that lives in the house that bullied me waves at me while I'm walking home
>nope.jpg
>find a social media account of the bully
>tell her to stop waving at me and to leave me alone
>bully makes her social media accounts public
>post a photo of her boyfriend with "I can't wait until he gets me pregnant"
>kek

I'm sorry, but is she stupid enough to believe that I actually like her and is trying to send the message to back off or is this a mere coincidence? I seriously hope is the second one. I don't think she's that stupid.

Hey, I'm trying to understand thermodynamics from the four related chapters in physics for scientists and engineers. What's the best way to go about it - do it slowly and complete all exercises then move to the next chapter or to read the 4 chapters and then do the exercises strictly? Thanks

how would you approach this?

Is Apostol's calculus worth going through if I am an engineer?

>>9858026
*If I want to be an engineer

Brainlet here, how do i find the roots of
x=2ln(x^2+1)

What's the speed of electricity? What's the speed of electricity through an inductor (of any material)?

Why medieval/pirate shirts have those strings on the chest? Did it serve some purpose or was it for decoration only?

>>9858164
x=0 is one; you need to find the other two numerically (0.5800558889626750 and 8.662482119217619).

>>9856698
Gold is a noble metal, it does not oxidize easily (to form other components) and "prefers" Au - Au metallic bonds.

How did animals develop skin sensitivity to extreme heat? Was it the sun?

>>9856618
How did fruit bats grow to occupy an ecological niche that was already occupied by birds?

>>9858025
Wolfram is retarded with respect to simplifying that expression but yeah they're the same

>>9858026
no, do stewart or boas

>>9855388
Every pop sci person loves Gödel because he shows there are true statements that aren’t provable. Are there likewise false statements that aren’t provable?

>>9859023
>Are there likewise false statements that aren’t provable?
take any true statement x that isn't provable, then not x is false and not provable

>>9859028
So why all the focus on “true” statements? It’d be more pedagogically helpful to say “there are statements whose thuth or falsehood is not provable” lazy writing maybe(?)

i'm brainlet, how do I find the Y values for the key points? I understand how to get the X values, but my professor did a terrible job of explaining how to get the Y values

>t. 22 year old brainlet taking trig

>>9859044
What you are saying adds no information, so there is no reason to say it. It's funny that you complain about popsci but get mad when expected to make the most basic of inference

>>9859053
Happy to be your clown.

How can space clouds have alcohol? Can someone explain to this brainlet how it came to be? I have read some stuff about it but I still don’t get it.

>>9857938
Cringe.

>>9855388
Is there a simple(not counterexample) way to show that a proof using intuitionist logic is not possible without LEM .
Simple like a truth table in classical logic.

Is it bad if I've had a monstrous vinegar craving all my life?

>>9856396
Montgomery - Experiment Design
Or maybe Daniels.
I'm sure there is the statistic test you are looking for.

In microeconomics:
Why in the slutsky equation the second term of the RHS has a minus in front and why in the slutsky matrix the ijth term is defined exactly with a slutsky equation with a plus instead?

>>9858642
Thanks a lot my dude

I'd like to buy myself a textbook and study something and teach myself. I am vaguely interested in cryptography and peer to peer networking / cloud (like telegram). Recommendations?

>>9855388
whats the use for gauss' law? it only works for perfect, closed surfaces as it states that: [eqn] \Phi_e = \oiint_s \vec{E}dvec{a} =\frac{Q_{in}}{\epsilon_0} [/eqn]
also, where does the [math] \epsilon_0 [/math] come from?

>>9855388
would really appreciate help with problem 8.66. I dont understand conceptually why I cant use the conservation of kinetic energy in this problem 1/2mv^2=1/2mv^2(final) and think of this problem as a truck hitting another truck with less mass while transferring all of its kinetic energy(truck with bigger mass having final velocity of 0"?

F=ma

Car moving toward me at 100 miles per hour but is not accelerating, so constant velocity.

By equation he should exert 0 force on me when he does hit me.

How come I still die?

>>9860724
newtonian forces are just a theory (a geuss), they're useful for making theoreitcal models but don't exist in practice

>>9860733
>but don't exist in practice
just like Newton's sex life!

I've recently begun working with a 16-input OpenBCI EEG helmet, and everything seems normal except that for some reason I'm getting absurdly high gamma bands. All others read normally, but I still think there's interference because it seems so out of place. I'm getting a reading as though I were dreaming or in REM sleep, but I am very much alert and awake. Possibly stress, but I don't believe the reading is accurate. Could there be something in my office to account for why only my gamma reading is anomalous? Thanks.

>>9860733
>don't exist in practice

Lol Physics.

Why is /sci/ so mean to beginners?

>>9860964
because it's 4chan, a hangout for misanthropes, recruiting ground for nazis, porn exchange, etc, what do you expect? the site's culture is about making people feel bad, why would /sci/ be different

>>9860964
it can be hard to tell a "beginner" from someone making an active decision to be retarded

>>9860989
sekret club XD

>>9860964
Advanced mathematics has limited application in most industry professions (ADVANCED mathematics, not whatever bugaboo shit you learned in MEC401) so people who know it have to berate others to feel better about themselves.

Given a circunference, with centre O and radius r, and two points, A and B, how can I construct a square that has a vertice in the line segment AO, one in BO and the other two on the circunference?

>>9861172
A and B are on the circunference

>>9855388
why woudld i need to know how to ask questioons smartly in stupid questioons thread

Alright guys, I can't wrap my head around this one for some reason...
I need to figure out the height and diameter for a cylinder with a volume of 1500cc where the height is 1.5 times the diameter. I think the formula is something like:
1500cc = pi x (d/2)^2 × h where h = 1.5 x d
How do I even start?

>>9859051
After you find values for x you just plug that shit into the orignal equation and solve for y.

How is baby rudin compared to the suggested analysis books in the image? I already know a decent amount of calculus

For context, I don't know how American or European universities work in terms of their class and points systems, so I apologize if what I'm saying is confusing. I'm in New Zealand.

My university requires students to pass 360 points worth of papers, where each paper is worth 15 points = 24 papers. Specific requirements vary between each major, but all majors require students to complete exactly 2 general education papers from a given list of courses with the 'G' suffix. This list of courses varies depending on which faculty your major falls under. I've completed 20 courses. I have 3 specific courses that I need to do as per my degree requirements, and then 1 more on top of that. My issue is that I was previously under the impression that some of the courses that I took marked as generals are not considered generals because they are science courses, and I am in a BSc program.

This essentially means I have 0/2 general education courses completed, and a course that I completed last semester is worthless and doesn't count toward my degree.. I wanted to try and talk to someone at my university and ask if an exception could be made in this instance so that one of the courses I've completed could be counted as a general, as I have failed several other courses while I was not doing very well at university, and am very close to the end of my degree. Has anyone done something like this before or have any tips apart from "dont"?

what does (|a+b|)^2 equal?

>>9861439
>what does (|a+b|)^2 equal?
(a+b)^2

>>9861383
My prof with a PhD in topology knew it and had a bit of interesting things to say about the book and Rudins life.
He didn't know who Munkres was or that he had a topology book so that should be telling as well.
Nice old dude in his 60s or so that worked at Lockheed when he was younger so I think he knows his shit.

>>9856816
>>9856828
I am almost certain now these are potassium chloride crystals due to the crystal pyramid structures in pic related for KCL crystals. i realize I didn't give a clear pic of the crystals in question but upon further up close inspection I noticed a crystal with this exact pyramid shape. I doubt HCL crystals as it should be below freezing for that to occur but it did rapidly drop from 400 F to room temp over the course of an hour. Tartaric acid crystals should have a rainbow sheen when introduced to polarized light and these crystals didn't. Tartaric acid crystals also shouldn't fully dissolve immediately upon contact with water or acetone like these crystals do. I guess the only way to know for sure is to burn it and see if it produces a blue flame.

>>9861946
whoops forgot pic

>>9860250
The epsilon term is just a constant that makes it 'work'. Alternatively, Gauss law could just say that the charge enclosed is proportional to the total flux and it would mean exactly the same. As for its use, I'm not an engineet but it's a great and important theoretical result that means that the total flux over any closed surface (not just a sphere,but anything homeomorphic to it) depends solely on how much electric charge is inside, so that any electric field a charge can create,it will create an equal and oppositely oriented field too

>>9861383
It's good, a standard reference, but me and almost everyone else says that it's only useful if you're following a university class concurrently. Otherwise, it's a bit dry, and missing a lot of explanation and motivation, prioritising neat and elegant arguments over illuminating ones. Tao is better in this regard.

>>9861264
>1500cc = pi x (d/2)^2 × h where h = 1.5 x d
= pi × d^2/4 × (3/2) x d
= (3/8) × pi × d^3
=> d^3 = (1500×8)/(3×pi)
= 4000/pi
=> d = (4000/pi)^(1/3)
~= 10.839 cm

This is not usual matrix multiplication, normally from R^n -> R^m we would have a linear combination of n basis vectors not m basis vectors. This just seems nonsensical to me

spivak calculus on manifolds page 3 :v

>>9862613
brainlet

>>9862613
R^m is spanned by m basis vectors. How/why would the image of the transformation be spanned by n?

>>9855388
>Is there a way to click on "I'm not a robot" and always get the checkmark without needing to select all images with [x]? If not, is there something that will click the images for me?

You mean... like... Some sort of robot?

>>9862659
Yeah I realized this right after. For some reason I was thinking it was talking about enumerating thought the components of each e_i

Why do we need windows in modern buildings??
Modern buildings have their own ventilation system. There is no vitamin D absorption through glass. The energy consumption of LED lights is less than the one from the heathing/cooling needed because of the reduced thermal performance of the walls due to windows. They are weak points for intruders.

>>9862398
Thanks!

How would I start to prove that the indicator function for the rationals is not Riemann-integrable? I'm in 1st year calc and I can't seem to do anything with the way the integral is defined (the limit of a sum of the subintervals of a function)

>>9863068
Show the upper and lower sums converge to different values.

Is azonine aromatic?

Taking Complex. I need to find the principle part of [math]\frac{1}{e^z-1-z}[/math] at z=0. I got up to [math]z^2(\frac{1}{2}+\frac{z}{3!}+\cdots)=z^2g(z)=1.[\math]. If I write the algebraic inverse of g I yield a regular power series and I write as
[math](a_0+a_1z+a_2z^2+\cdots)g(z)=1[/math]. I figured the first coefficient is just 1/2. How do I figure out the second coefficient?

>Fact: every drop of water on the planet, at some point in time, has been some crtitter's PISS.
is this really true? is it unthinkable that the ocean is big enough and that life is small is enough that there is water that hasn't been piss?

What is the mass matrix for this configuration in small oscillations?

I'm between:

[math] \left(\begin{array}{ccc} M & 0 & 0\\ 0 & M+m & 2lm \\ 0 &2lm & ml^{2} \end{array}\right)[/math]

And:

[math] \left(\begin{array}{ccc} M & 0 & 0\\ 0 & M & 0 \\ 0 & 0 & ml^{2} \end{array}\right)[/math]

First row is left block's movement, second row is right block's movement and third row is the angle between the m mass and the vertical. I'm more inclined on the first but then I get a huge polynomial when I calculate the determinant of the [math]-\omega^{2}M + V[/math] matrix so I can't obtain the frequencies analitically.

Are chemical reactions all about sn1,sn2,e1e2?
Why is it so difficult to discern the quality of molecule and it's substrate?

Engineering student here, is it common to refer to two books at the same time for a single class? Because my prof suggested two. Am I supposed to complete both?

Is the solution of a linear matrix diffeq always be a subspace of dim n where the matrix is n,n? What if the matrix isnt invertible/the rows arent linearly independent? Then you only really get less than n equations in your differential system of equations and the dimension of the subspace of solutions is lower...
How could x' = [[1 1][1 1]]x have two dimensions of solutions? I can only get x(t) = e^(2t)

wtf is the point of complex analysis

If x^y is defined as exp(ln(x)*y) then wtf is 0^y

>>9863617
lim x-> inf e^(-x)

>>9860989
xDDD /pol/=/b/=/sci/ , because they exist on the same website

You should know that 95% of 4chan boards are calling to removal of /pol/ and /b/ since m00t days, these boards are cancer

>>9863632
>You should know that 95% of 4chan boards are calling to removal of /pol/
Speak for yourself.

>>9863068
as other anon suggested, in any (and i mean ANY) interval containing real numbers, there must be at least one rational and one irrational number. In particular, the sup and inf of the indicator will always be 0 or 1 respectively, so the lower/upper sums will be different.

>>9863699
>as other anon suggested, in any (and i mean ANY) interval containing real numbers, there must be at least one rational and one irrational number.
[pi, pi]

>>9863716
containing real numberS, that is, at least two, dipshit

Why do our dreams allow us to do abstract things like emails and browse the "net"?

*of course you don't really do these but that is what happens in the dream.

>>9863115

>>9860724
The acceleration comes when the car hits something else, it goes from 100 mph to some lesser value in some finite amount of time

This a force is made because an acceleration is made

>>9859142
alcohol (ethanol) is a pretty small simple molecule. Pretty reasonable for it to be formed by chance. there's shitloads of radiation in space so I'd assume loads of carbon hydrogen and oxygen radicals are being formed all the time. All you'd need is methane (common) and oxygen (common) with radiation to cleave the bonds.

At this point in my life, it's too late for me to pursue a career in anything related to math or physics. I work in healthcare but I recently started becoming really interested in these topics.

I figured that my job doesn't have to define who I really am. I can work to make money to feed myself but, in my spare time, I can learn and improve myself.

Is there anybody here who is a "stay-at-home engineer" or whatever? That's basically my plan. Is there anything I can buy that will allow me to be creative at home? I've never even created a battery before.

>>9863840
At this point, half of engineering is just coding. You might do well learning Python and making your first few programs (maybe something like a sudoku solver, or something of the like). You will invariably need some math to do anything meaningful however, but don't be discouraged, you can pick it up as you need it, and it is not in general very "high level" anyways. A book like Discrete math by rosen (which you can download for free on libgen.io or .pw) has everything you need plus a ton of programming exercises too which can compliment you learning of Python.

If you eventually want to create something actually physical, then you might want to get an Arduino. If you think you'd get more enjoyment out of creating something like a robot arm or something that moves that you can program (and have some extra cash lying around), Lego mindstorm is probably the funnest/most accessible.

Help me pls, I'm searching for a surreal artwork that was posted on /sci/ a week ago.
>>>/wsr/535935

Maybe that OP is still here in this thread.

>>9860721

It's a trick question. Sort of.

The net force on the hopper is always zero, so the velocity is unchanged!

In the beginning it's traveling at its initial speed. The mass of the hopper is balanced by the reaction from the track. There is no friction. Nothing else is relevant.

As sand drops out, energy and momentum are carried away by the sand and presumably dissipated in contact with the Earth, so the momentum and KE of the hopper decrease. The sand is dropping directly out of the bottom, so all that would really change is that the reaction force changes, and since there is no friction, this has no impact. But the sand is not being ejected out of the back in a rocket scenario, it's just dropping out under gravity. With no frictional forces acting on the hopper, it continues at the same velocity.

As soon as friction enters the fray, the situation is entirely different. Of course, in that case you still could not use KE or momentum conservation (at least naively) since energy/momentum are being lost by the sand.

>>9863593

It's quite common. I've seen professors insist upon a textbook as the overarching course 'bible', but also suggest some more specialist texts for certain parts. Similarly, a book might be good for 90% of the course, but lack a chapter on a specific element (or the chapter is useless), so you need a second book to bridge the gap. Conversely, you might have an otherwise mediocre textbook that has a few salient sections that are really good (this happens quite a lot), so you use it only for its good bits.

And even if both books are good, every book has a different style. I have had many occasions where I read about a topic in one (otherwise great) textbook and didn't really get it, but read about it from another textbook, and because of the way it was explained, it made a great deal more sense purely because it was communicated a little differently. Sometimes professors offer a bunch of good books and let you decide whose style fits you best.

If the books are for the same class, then there should be tons of overlap, and you can try them both to see which one you like best. And if it lets you down along the line, then use the other. Indeed, if you are really keen, it's good to read chapters about the same subject from multiple sources to get a really good overview.

Can you make a laser beam that’s bright and visible but stops at a certain length? Like can you “limit” the length of a laser?

Im basically asking if you can make a light saber or a facsimile of it

>>9863840
how old are you?

>>9862875

Psychological importance - natural light and the ability to see outside is very beneficial for mood. I imagine you could technically produce the same impact by either simulating the outside world or using cameras (like that airline is trying). But whether that is any cheaper I don't know. It would allow for a certain level of mood control - I imagine that future houses will have lifelike simulated exterior environments so that you can pretend you live on the waterfront or in a forest. That could actually be superior to white trash neighbours.

Design considerations - We're like to design stuff with windows, so there's a design inertia around it - it looks 'normal' to have windows, especially in skyscrapers.

Combining the two points above - windows can also be welcoming by providing would-be entrants with information. A house with blocked windows would seem intimidating, not to mention incriminating. There's a certain welcoming aspect of windows (though criminals obviously exploit this)

I think improving the thermal performance and security of windows is a simpler decision that trying to reinvent a pillar of human building design. However, I am sure that simulated exteriors are coming soon.

This discussion kind of reminded me of the 'Earth Room' in the film 'Sunshine' (https://www.youtube.com/watch?v=21sBDkk7M2c)) where they try to eliminate feelings of entrapment and claustrophobia by simulating 'freer' and more human environments.

>>9864076
No

Well, you can't stop it abruptly. You could make it so that it dissipates in air at roughly the right length to mimic a lightsaber, but really you'd just get a gradual fade and it probably wouldn't be very impressive.

Maybe you could have two laser beams at angles which would meet and generate a plasma in air, (and repeat this lots of times to make a line), but I don't know how you would contain all of that magnetically with just the hilt. Or maybe you could eject a fluid in a certain way and then heat it (sort of like a flamethrower); but it doesn't seem practical, nor would you get smooth motion on the swings ... or effectiveness on windy days.

A far simpler way to make a lightsaber would be a heated/electrified filament (https://en.wikipedia.org/wiki/Electrosurgery).). It's just a sword with increase penetration, which covers the basics of a lightsaber. And with a thick enough core, I suppose it could block bullets ... but there are simpler ways.

>>9864052
'elp me.

>>9864213
otto rapp's "deterioration mind over matter"

>>9864275
Deterioration *of* mind over matter.

>>9864275
It's exactly this. Thank you so much!
Without any of these keywords it seems impossible to find.

Are there any non-inductive proofs that prove addition is commutative for naturals?

>>9864375
why would you care about the naturals if you dont believe in induction?

>>9856698
>How do the bits of gold find each other?
Bacteria. They absorb minerals and chemicals and gold gets secreted through the cell wall and over time it creates veins.

>>9864066
Thank you very much!

>>9863724
>>9863115
idk why you factored out the 2, it seems superfluous. I just saw that your answer doesn't agree with wolfram alpha, at least mine does. Check it...

yo can someone debunk this shit

are europeans just domesticated neanderthals?

https://atala.fr/chapter-1/

>>9856396
Sounds like you want to assess for statistical interactions of two factors. Look into two-way ANOVA

>>9861390
Just email someone like an advisor.

how the fuck do I git gud at factoring? I'm in pre-calc and up to this point I've been able to pass the year despite getting a 60% on the "factoring" chapter in Algebra 2 (and 1.)

Just had another "factoring" chapter last week in pre-calc that requires canceling out factors in rational equations to then solve and graph. This weeks chapter I passed again but I don't want to keep putting off getting good at factoring polynomials.

Note: by getting good I mean it takes me a lot longer than most other kids in my class and on tests that focus purely on factoring I tend to just kind of fuck up but then do okay when it's just part of a much larger thing (meaning the polynomials tend to be a bit less complex.)

pls help /sci/

>>9864866
Lol there's like five ways to factor shit. Get gud.

>>9864866
keep practicing until it's no longer an issue. there's not much else you can do

>>9864725
welp, i put the 3 on top instead of the bottom, whatever

>>9855388
what's the name of this effect?
>A fluid changes its temperature when pumped through a small hole

in the coming semesters I'm going to be taking Calculus II and Calculus-Based Physics II: Electricity and Electromagnetism.

Everyone and everything tells me these two classes are brutal.
I can't, however, find much information on why.
All I've been able to ascertain is that integration is a non-trivia PITA and Calc II is all about them, and I assume Physics II involves them a lot too.

Can you guys tell me why people consider these two courses to be difficult so I know what to study up on before I take them?

>>9865872
YOU SHIT AT STEM< SL

>>9865889
t-thanks you too

>>9855388
>Is there a way to click on "I'm not a robot" and always get the checkmark without needing to select all images with [x]? If not, is there something that will click the images for me?
Short of paying for a proxy service where people in the third world solve the captcha for ya, the next method I can think of would be to find "virgin" proxies. Captcha increases its difficulty based on the frequency of Captcha requests an IP makes, so you're more apt to get the "okay, you clicked, and are not a robot" response if you are on an IP that rarely, if ever, uses Captcha.

It does seem there should be some way to "fake a positive response", but it's beyond me. Ya might check with >>>/g/.

>>9865872
If you are "that smart guy" you shouldn't have a problem.

I'm just assuming most people on this board are "that smart guy"

>>9865872
>what to study up on before I take them?
Calculus II and Calculus-Based Physics II: Electricity and Electromagnetism.

Is there any textbook that covers Plant Biochemistry (that is above undergraduate level)? Please help I'm looking for something modern but most textbooks for plant biochem are 20 or so years old.

I have covered all of Lehniger and Voet, also Zeiger and 3rd edition of Heldt so I'm set for something more specific in the field of phytobiology

>>9866506
Oh also I have studied many texts involving general natural products total synthesis as well as some biosynthesis, natural products and their biosynthesis etc

Why is it so hot underground?

Like the major borehole projects all report 200 degree+ ambient temperatures once you get a few km underground, in spite of the fact that they're only a fraction of the way to the mantle.

Do you need to know a programming language for engineering? And if so, what's a good one to learn?

Never really put much though into either of those, but just recently realized I was interested in aerospace.

>>9866636
Dense rock is a much better thermal conductor than loose sand or soil. So the topmost layers account for a disproportionately large fraction of the total temperature difference between the mantle and the surface.

>>9865810
https://www.reddit.com/r/askscience/comments/2tjtz4/what_causes_things_under_pressure_to_heat_up/

I want to build my own liquid cooling garment using "cutting edge" research.
The problem is that I have no idea what to search for.
Wikipedia says they just use PVC or silicone and everything else is just a way to get the tubing to wrap around your body, but that can't be everything, can it?
What about materials to increase the conductivity between the underlying skin/cloth and the tubing?

>>9867118
if it's too conductive it'll be too cold and uncomfortable

>>9867258
Then you can just regulate the temperature of the water

>>9867265
i don't think heat conductivity is an issue. things like copper heatsinks like for pc watercooling are for cooling one small very hot component but for a garment you want the cooling to be spread out anyway and other things like flexibility and light weight are more important than being able to cool you down very rapidly unless it's for an incredibly niche use case.

>>9867303
>heatsinks
waterblock i mean

>>9862674
I laughed way too hard at this, thanks :')

>>9855388
>Is there a way to click on "I'm not a robot" and always get the checkmark without needing to select all images with [x]? If not, is there something that will click the images for me?
no, what you can do is clear your google cookies and have a high success rate of solving them, this way you'll get the checkmark less often and fewer shitty slow fading ones

>>9867517
Dun think clearing cookies works anymore, seems they started tracking server side. Once one computer on the network here starts getting the complex captchas, they all do.

Hate it. Pure security theatre. There's nothing about those extra steps that'd make it harder for an automated system to solve - it only makes it harder on people.

>>9867303
>things like flexibility and light weight
well shit, now how am I supposed to look for research? Do people publish test results on ergonomic designs? How do people even benchmark one design against another?

What does "specific" in specific heat transfer, specific weight, etc. mean?

>>9867517
>>9855388
It happens with a VPN too, sometimes it wont load at all.
tldr fuck google

Okay, I know/knew almost nothing about electricity (like even the difference between a volt and an amp) so I picked up some book on AC theory at a yard sale on a whim.
Can someone explain to me how pic related makes sense?
I see how they get 59.65 from 1/(1/85+1/200), but is there some logic behind why the figures differ in the text and the diagram, or is it just an erratum?

>>9868012
It means it's not changeable, it's a constant
Like the specific heat capacity of water

>>9868085
Erratum. They used the values from the previous section.

>>9855388
No question. Just an ad lib, /sci/ style.
>Step away, my [blank] is [blank]

Question on diff eq. hw: "Find f(t) if F(s) is s/(((s+2)^2) + 3)"

I expanded the denominator to s^2 + 4s + 7 leaving me a homogeneous equation of

fh(t)=Ce^(-2t)cos(sqrt(3t)) + De^(-2t)sin(sqrt(3)t)

How do I find the particular solution or am I totally off here? I tried partial-fractional decomposition and comparing to the Laplace transforms for cos(bt) and e^(at)cos(bt) but neither of those worked out nicely.

>>9855388
How can anyone make any argument against nurture in a Nature vs Nurture debate when everything down to our very DNA is a product of our environment and is incredibly susceptible to said environment?

>>9869515
because once you are born, your dna does not change

>>9869516
What about mutations and epigenetics? Twin studies show differences.

>>9869535
what are you trying to say here. people's dna does not suddenly mutate and turn them potato. therefore genetics/nature certainly has a significant amount of impact.
people with tall parents are usually tall. people with white parents are white. etc. how could you deny that nature has no effect at all?

>>9869539
Because even these traits are a product of environment. What mothers eat can affect birth and dna. Your nutrition and physical action as a child affects your final height and complextion. If you truly subscribe to the evolutionary model, this is all mutable. Allergies come and go. DNA is just really weird protein and screws up easily and naturally. So what is really one's nature?

>>9869549
you are missing the point of nature vs nurture, i think
evolution has nothing to do with this. evolution is not relevant to the lifespan of one individual
if the mother is deficient in nutrition, you will have a stunted child, yes. that is a point for nurture
but if two mothers have sufficient and similar nutrition, differences in height are due to the nature of the child. a point for nature.
clearly some blend of nature and nurture determine the final height. the question is how much.

>>9855388
What percentage of genome must be different between 2 individuals in order for them to be not only different individuals, but different species?

>>9869515
This is kinda like saying everything artificial is natural, because it's all the result of mankind's natural evolution and tendencies. It's simply fiddling with semantics.

Nature vs. Nurture is really regarding how much is fixed at birth vs. how much is dynamic. Potential vs. Actualization, Hardware vs. Software.

/sci/, as part of 4chan, tends to lean towards nature, and it's true, to oversimplify it, while a VIC-20 PC from the 70's might be able to do all the same calculations that a modern PC can do, it can't do them in the same period of time. Humans with various genetics are in the same boat, even if they have more potential to fill niches, since processing speed isn't the only value involved.

On the other hand, we are rapidly approaching the age when we can choose our own hardware, at which point the debate will be moot. It will no longer be nature vs. nurture, but much like with computers, one design vs. another.

>>9869778
Taxology isn't, currently, defined by genetics. It isn't a hard and fast system, primarily because it was in process well before DNA was discovered, and people seem to be too lazy to go back and do it all over again. (Well, that, and we don't have genetic maps of every creature on the planet to compare.) There's also the question of "can breed" vs. "will breed", and capable of inception vs. capable of bringing to term. These two, for instance, can artificially conceive, but not bring to term. Morphology, mating seasons, behavior, and other factors go into species and subspecies definitions as well, so it's a mess.

Whether two creatures can genetically conceive, however, isn't determined by a specific percentage of genome differences either, but by whether key pairs within the genomes can link up, and that varies wildly. For instance, while these two can conceive, despite their drastic morphological differences, there's species of birds that are physically identical in every way, save for a fraction of a millimeter difference in average wingspan, yet they cannot interbreed (naturally nor artificially).

Having different numbers of chromosomes is not an absolute barrier to hybridization; similar mismatches are relatively common in existing species, a phenomenon known as chromosomal polymorphism.

Then you get into weird situations like mules and ring species - of which said birds are a part. The aforementioned two species of birds can't breed with one another, but they can both breed with another similar species. There's a lot of such ring species in the animal and plant kingdoms.

Suffice to say, the map of the tree of life isn't complete nor straightforward, and it has a lot branches that loop back on themselves. Until we comb that out, a lot of the image of that tree remains subjective. (Though, again, due to holdover science, probably even more so than necessity or lack of information would dictate.)

>>9869880
...and of course I forget the image.

I have a 120v US lamp plugged into 120v mains. It has a LED 4.5watt "45 watt" bulb rated for 240v european mains.

So the LED bulb works. Why? I always thought LEDs needed exact voltages/ amps in order to light up. It seems to work fine but I don't understand why. Will it degrade it's lifespan or catch anything on fire?

>>9869488
> How do I find the particular solution
You'd need to know the initial values, f(0) and f'(0). The transfer function alone can only give you the homogeneous solution.

>>9870058
The actual LEDs need a few volts DC. The rest of the bulb converts AC mains to the required DC voltage, and regulate the current.

Switch-mode PSUs don't particularly care about their input voltage or frequency. Plugging a 110V bulb into a 240V supply might cause components to fail due to excess voltage, but if the components hold up the bulb would work.

>>9870121
So I just leave it then? What do I do with the 's' in the numerator?

>>9869883
>you're a big guy
>for you

>>9870206
> What do I do with the 's' in the numerator?
That's what gives you the cos() term.
L^-1{(s+a)/((s+a)^2+w^2)} = e^-at.cos(wt)
L^-1{w/((s+a)^2+w^2)} = e^-at.sin(wt)
Because the transform is linear, you can decompose the function into multiples of the above terms and find their inverse transforms separately.

a=2, w=sqrt(3)

s/((s+2)^2+3)
=s/((s+2)^2+sqrt(3)^2)
=(s+2)/((s+2)^2+sqrt(3)^2) - (2/sqrt(3))*sqrt(3)/((s+2)^2+sqrt(3)^2)
L^-1{(s+2)/((s+2)^2+sqrt(3)^2)} = e^-2t*cos(sqrt(3)*t)
L^-1{sqrt(3)/((s+2)^2+sqrt(3)^2)} = e^-2t*sin(sqrt(3)*t)
=> L^-1{s/((s+2)^2+3)} = e^-2t*cos(sqrt(3)*t) - 2/sqrt(3))*e^-2t*sin(sqrt(3)*t)

>>9870340
Thank you kind anon

If I use a gyrator to turn a voltage source, say a 9V battery into a current source will the circuit supply a maximum of 9V, or can it supply higher voltages at lower currents?

>>9870666
A gyrator can't produce a voltage above that used to power the active element (typically an op-amp).

Audio must travel via electricity right? So If I frayed an audio cord and put a multimeter on it would there be increased electricity when sound is traveling through it?

>>9863611
https://en.wikipedia.org/wiki/Branch_point

>>9871319
Audio is information. A signal. Anything which can transfer information, or a signal, can carry audio. Electricity is one convenient form, and the speaker on the other end is a device (an electromagnet which vibrates a surface) that operates on electricity.

If you frayed an audio cable and placed the probes of a multimeter on both cables, you'll see the voltage changing wildly.
Connect it to an oscilloscope, and you'll see the audio waveform.

>>9855388
I've been NEET for 7 years and haven't really used my brain for much. I'm still good with abstract logic concepts but I'm terrible with numbers themselves. is there any way to fix this? I was thinking about going to CC for math but i don't want to suck dick at it I just want to go because I can get free shit

I remember my physics book in high school had an image that said until Newton, people believed that if you threw things they would just go straight and at some point fall vertically.
Assuming people weren't complete retards up to that point, whats the logic behind that? Or my book was just making stuff up?

What the FUCK does it mean when a virus is "SUSCEPTIBLE to isopropanol"? Does it mean that the isopropanol kills the virus or what?

is "being susceptible to" = this [insert chemical/disinfectant] is able to inactivate/delet the virus?

Thanks in advance

I want to learn botany and plant taxonomy for recreational purposes.
Which are some recommended books to learn about those disciplines?

>>9872452
> people believed that if you threw things they would just go straight and at some point fall vertically.
Pic related is from a Treatise on ballistics by Tartaglia in ~1531. I think Gallileo pretty much fixed that. The inverse-square law was discovered by Newton but isn't particularly relevant for terrestrial ballistics (you can assume that gravity is pretty much constant until you get to altitudes which weren't achievable until the 20th century).

>>9860724
The car accelerates (negatively) when it hits you. You can also think about it in terms of energy: the car has kinetic energy 1/2*m*v^2 before it hits you, then it imparts some of that energy when it hits you (Energy imparted=Work=F*d). Or you can think about it in terms of momentum. The car has momentum MV before it hits you. If there are no external forces, MVi for the car will equal MVf for you plus MVf for the car

I don't know calc yet but every single time I see summation notation in a textbook I get very afraid of it and give up reading because I assume I'll have to know calculus in order to go further into the textbook. what I want to ask is: does summation notation has anything to do with calculus? I also would like to know where can I learn and practice summation notation because I really want to internalize it

>>9872641
> does summation notation has anything to do with calculus?
No.

What different types of math must I be comfortable with to get into quantum mechanics? I’ve already been through stats and calc 1 but it was years ago. I’ve been doing all the khan academy courses all the way from the bottom starting with algebra 2 so I can get my mind back into thinking he right way and I plan on going all the way through calculus again so I remember everything. What other things should I know before I dive into the textbook I have (griffiths intro to qm)?

>>9872641
https://simple.wikipedia.org/wiki/Sum#Sigma_notation

>>9872581
>Gallileo
That might have been it, I misremembered.
Still, so weird. Did these people never threw a rock or something? Or did they believe heavier things behaved differently?
This is probably related to the feather/cannonball fall speed thing, but that makes sense if you don't know about air resistance and is not so easily testable.

What's the difference between Allendoerfer & Oakley's Principles of Mathematics, and Fundamentals of Freshman Mathematics?

>>9872641
[eqn]1+1=\sum_{i=1}^2 1[/eqn]

>>9872641
>>9872716

I am under the impression that capital-sigma notation turns up in just about every branch of mathematics.

>>9872887

More examples:

[eqn] \sum_{n=1}^{4} n = 1+2+3+4 [/eqn]
[eqn] \sum_{n=1}^{\infty} n = 1+2+3+4+5+... [/eqn]
[eqn] \sum_{n=-3}^{4} n = -3+(-2)+(-1)+0+1+2+3+4 [/eqn]
[eqn] \sum_{n=0}^{2} x^n = x^0 + x^1 + x^2 = 1 + x + x^2[/eqn]

>>9873010

[eqn] \sum_{n=0}^{\infty} (-1)^{n} = 1-1+1-1+...[/eqn]

>>9859044

It's just one of those details that is hard to understand that it's possible to not understand when you understand them. It's clearly difficult to understand the incompleteness thms without good understanding of first order logic. The first incompleteness thm may be a pop.sci. favorite, but it also one of the most important thms in logic of the 20th century. No shame in learning about it!

>>9872641
Summation notation is used in calculus, calculus is not used in summation notation

>>9855388

Does learning pure math at high level bring you closer to schizophrenia? I would think a big part of pure math skill is being good at playing with abstractions, patterns, seeing new analogies/connections, attention to detail, imagination etc.. which in real life could manifest as paranoid thoughts.

>>9873016
just write 1/2 bro...

>>9873202

No. It's divergent. However, it's Cesaro sum is 1/2.

>>9873283
noob

Is there any reason to believe point particles are point particles instead of just really small?

how the hell am i supposed to sit while writing to not hurt myself?
My arms make a 90° angle with the table and my hands are placed at about 30 cm from my body for comfortable writing. Now i obviously have to look at what i write, and here is where the troubles come: while sitting, the distance from my eyes to the surface of my desk is 63 cm, so if i keep my back and neck straight (head leaning on headrest, as everyone suggests) what i'm writing is literally outside my FOV.
If i lean forward at my heaps and abadon the headrest of my chair, i can't keep my back and neck straight for more than 2 minutes. As soon as i focus on what i'm writing i bend my neck too much. A bookrest or inclined table have to be excluded because when you write your elbows have to make a =< 90° angle. Should i just embrace having back and neck pains at 20 and a badly fucked up back at 30-40?

>>9873353
Get a standing desk or one of those things that let you write while laying in bed or both. Humans were never meant to sit for long periods.

>>9873353
Get a clipboard or tablet to write on so you can periodically change positions, and make a conscious effort to do so.

>>9873377
But a standing desk doesn't solve the problem, if my elbows make a 90° angle, the relative position of my hand (the point where i have to look at) and my eyes is the same no matter if i sit or stand, so it'll still be out of my FOV
>those things that let you write while laying in bed
like? I can only find small and crappy laptop holders

>>9873379
Change positions to what? As far as i've read there's only 1 recommended position for writing

>>9873411
>Change positions to what?
Locking yourself in a single position is about the most stressful thing you can do for your body while awake, even if it is the "recommended" position.

Just keep moving and keep comfortable, you'll be fine.

I feel like a literal retard but can someone hold my hand through this one?

>>9873523
I can see why you feel like a retard. The problem is very poorly written and is very confusing.
Is this self study? If so consider finding a new book.

>>9873529
you right

>>9873573
however, here's my interpretation of the problem.
there's a camera at -f. It sees an object at l0. at a later time, it sees it at l(t). your job is to determine the speed of the object given l0 and l(t) (both of which are on the x axis)

>>9873575
yeah that much is gathered

how do i picture the bottom of a circle being at rest when its rolling with slipping.

>>9873583
ok, you understand how sines and cosines work right?

>>9873637
yessum

>>9873638
there's a right triangle with legs f and lo
that triangle is similar to the right triangle with legs f + Do. use this triangle to find the distance from the z axis to the object

there's a right triangle with legs -f and l(t)
that triangle is similar to the triangle with legs f + (Do -v*t) and the distance you found previously.

solve for v

>>9873299
Irrational attachment to the outdated continuum model

How does one go about fabricating amphetamine? is the process too complex?

>>9873299
>Is there any reason to believe point particles are point particles instead of just really small?
The lack of internal structure.

Why do we have to determine specifically the steps to the right, and not those up? Why can't the answer be [math]${221}\choose{111}$[/math]?

Why do we have to determine specifically the steps to the right, and not those up? Why can't the answer be [math]{221}\choose{111}[/math]?

Why do we have to determine specifically the steps to the right, and not those up? Why can't the answer be [math] {221} \choose {111} [/math]?

>>9873457
>Just keep moving and keep comfortable, you'll be fine.
that's kinda what i've always been doing and now i have back pains and irreversible back injuries. What my body naturally tends to and feels "comfortable" to me seems to actually be pretty bad for me

What the fuck is a logarithm? I know how to use them to solve exponential equations and so on, but if someone asked me exactly what it is I'd be stumped.

>>9874065
It doesn't matter whether you determine the U's or R's. [math] \binom{221}{111} = \binom{221}{110} [/math], as you can easily verify by considering the definition of [math] \binom{n}{r} [/math].

I'm sorry if its not exactly the appropriate place to ask this but i wouldn't want to kill a thread here and /adv/ is too retardo.

My grades on STEM-related subjects during HS were average (mostly due to ADHD, been treating myself with sertralin and omega oils with very nice improvements) and i dont have many extracurricular activities to show. Would there be a way to improve my curriculum post HS so i could get to an good uni on physics/chem/engineering ?

Which hormone is responsible for erections? Any way to decrease production?

>>9874233
the inverse of the exponential function

>>9874285
If you have any kind of experience with application processes/criteria to share i would be very grateful.

>>9874377
testosterone
chemical castration

How fast do primes diverge? For i going to infinity and p_i denoting the ith prime, is p_i+1 / p_i = 1 or 0?

>>9874377
Just read the Wikipedia entry, you should find clarification there.

>>9874618
yes, in fact p_i grows like i*log(i)

If I want to read Jung, should I start with Freud or jump right in? Is there a book or books that are essential towards understanding the rest?

>>9874685
Freud is a sexually obsessed pseud. Jung salvages all his decent ideas and turns them into something actually resembling science.

>>9874710
Right, but I want to be able to see where Jung is coming from. "Where do i start with Jung?" might be a better question.

f(x) = 1 - 1/x in the domain R - {0}.
Is this function bijective?

>>9875612
What have you tried?

>>9875612

1 is in R\{0}. Can we obtain x such that f(x)=1?
Since f(x)=1 - 1/x, we must have

1 - 1/x = 1

but since we have 1/x != 0 for all x in R\{0} we cannot satisfy the equality, hence f(x) is not onto R\{0} and therefore cannot be bijective. f(x) is injective though.

>>9875792
But f(0)=1-1/0=1-0=1, so doesn't this mean f is bijective?

Where can I read about the double slit experiment without some bullshit theory about the observation effect?

>>9875825

1/0 is not equal to 0

>>9875612
>>9875792
>>9875825
to say or find if it is bijective you first have to specify the codomain retards

>>9855388
How to increase my IQ?
(125-130 brainlet)

I want to learn organic chemistry.
What's the best way to learn it?
I was in class and wrote the notes.
But they help me jack shit, because Working with them I feel like something is missing.
Homework sucks and those profs think we have some profound prior knowledge although in my undergrad, we are only required to pass the exam.

Is a 12000 pages of organic chemistry while relying on the class's curriculum a good idea?

>>9875825
>1/0
oh shit nigga

>>9876153
type bigger numbers

>>9856480
>But let's say I have down the basic topics of factorizations, eigenvalues, determinants. The section on linear transformations lost me.
Holy shit that book must be complete cancer.
Throw it in the trash and pick a good one like Axler's.
Also, watch 3blue1brown's videos.

I want to get a compete blood panel testing (whatever the terminology is) before I start a diet to see if I have any deficiencies, and also so I have a baseline to compare to later in the diet. I take those two-a-day vitamin gummies and a vitamin d supplement. How long would I have to abstain from taking those for my levels to get back to "normal" for the absolute baseline?

>>9876097

I assumed domain = codomain since he didn't specify. But you're right, I shouldn't do that. It is not surjective with codomain R\{0},but it is surjective with codomain R\{1}, lol.

>>9876153

Just do math seriously. No one will tell the difference.

What do you think is the point of knowledge if it has no practical applications?
Don't get me wrong, I am not one of those "muh applications" engineers, I like math and like to learn about stuff even if it isn't useful in real life, but I can't explain the importance of working on abstract stuff that isn't related to the real world at all. The only argument that I can think of is that applications can't arise without having done some pure, abstract work before, but that would imply that pure science is useless and applications are actually the only things that matter, which I don't agree with but can't refute in any way.

>>9877153
Things with practical applications often arise, either directly or indirectly, from discoveries which, at the time, had no practical application.

Sometimes these things are simple thought experiments, never intended to have practical applications or even reflect reality, or even things simply designed for entertainment.

>>9877153

>What do you think is the point of knowledge if it has no practical applications?
>The only argument that I can think of is that applications can't arise without having done some pure work before.

I would think it's more often the other way around. Pure work gets meta-motivated from actual real life applications. Pure work could be generalization of concrete real world problems. The need to calculate N in context #1 inspires the mathematician to find a way to calculate N for context #1,#2,#3,#4,.... Then you solve your original real world problem and then some more associated pure ones, getting pure work as an add-on.

Also, I would guess doing pure work does not feel like it does not have application to a mathematician even though it is often true. A mathematician feels the need to get the solution to some thought up abstract problem as important as a real world application, because they have learned to think of abstract ideas as though they are real. That is Platonism in mathematics, and I would believe most mathematicians need to think that way to be able to do research, even though they might have a different opinion on the philosophy of mathematics.

>>9877295
So if I'm getting it right, what you are basically saying is that research in pure sciences is important because it may inspire applications later on? Wouldn't you be basically admitting that knowledge is only useful when it has real life applications?

>>9877340
> A mathematician feels the need to get the solution to some thought up abstract problem as important as a real world application
But when it comes to funding, who cares if the mathematician thinks it is important? If his work had no real life applications, neither directly nor indirectly, wouldn't it be a waste of time and money?

How do I get better handwriting?

>>9877549
legally change your name to whatever letters you're best at writing

>>9877519
The point is, you never know what's going to be useful later, and some discoveries lead to other discoveries. Sometimes to entire new fields of math with multiple applications.

Plenty of mathematical examples of that - we use discoveries from the 16th century today that didn't even become useful until 3-4 centuries later - though usually the return time isn't quite that painful.

I'm not sure why the One-Electron Universe thing keeps coming to mind. I suppose, on /sci/, it's actually a bit detrimental, as folks here seem to think it was a real theory rather than a deliberately absurd thought experiment that John Wheeler actually bothered to do the math for. In any case, the mere mathematically musing led his student, Richard Feynman, to an approach that allowed for several discoveries with actual applications in the LHC's research (and a nobel prize).

There are certainly less esoteric examples though.

>>9877880
>trying to convince someone who doesn't want to be convinced
anon don't waste your effort

---Part 1/2---

>>9877519

>But when it comes to funding, who cares if the mathematician thinks it is important?
Luckily for the mathematician, most math can be done with only a paper and a pencil. And since math matters to the mathematicians, they do it still if nobody else cares about it.

>If his work had no real life applications, neither directly nor indirectly, wouldn't it be a waste of time and money?

It probably mostly not feel that way for the mathematicians. It's hard give an easy answer to why, and there may be different answers for different mathematicians.

I have no doubt that there exists mathematicians that believe that the value of math ultimately is measured in useful application. But application can happen hundreds of years after conception of the particular math, thus not experiencing useful real world application in their lifetime might not be devastating at all. Some may even feel that the longer time it takes before their math get used in applications indicates how long ahead of their time they were. Also, there is indirect application, the scenario where some piece of math is useful for creating some other piece of math. If the last piece of math has applications, then the first piece of math was indirectly useful in applications.

A certain breed of mathematicians may insist militantly that they are trying to do the most pure and useless math, trying to maximize abstractness and beauty. They may feel that usefulness harm the beauty. A classic example is G.H. Hardy which said

"I have never done anything 'useful'. No discovery of mine has made, or is likely to make, directly or indirectly, for good or ill, the least difference to the amenity of the world."

despite devoting his life to pure mathematics and clearly having no regrets about it.

I am not sure what the complete opposite of G.H. Hardy would be, but I am guessing you won't find many of those in your usual math department at university.

>>9877942

---Part 2/2 ---

At last, there is the math that will be forgot. The math that never even will appreciated or built upon by other mathematicians. Published and then skimmed over by a dozen people. Some mathematics is just bad, and it will die for the same reason your shitty childhood drawings did. But you liked drawing those things, right? It felt important.

If diamorphine is like stronger morphine, then is there something like stronger diamorphine?

>>9878397
Trimorphine

For someone pretty bad at calculus and pure maths, is it an absolutely horrible idea to take Calc 3 and Linear Algebra at the same time?

I got a C- in calc 2 and I have to retake the course for my stats degree, so im thinking of retaking calc 2 with calc 3

HOW does this make any sense?

>>9878734
[eqn] \frac{1}{a} = \frac{a}{a^2} [/eqn]
HOW does this make any sense?

>>9878734
multiply numerator and denominator by sqrt(3)

How do I get over my climate change anxiety

>>9878761
Yeah it does not makes sense, just put 0 into a

>>9878778
Okay. Second question: what's the point of this whole practice?

>>9878800
so you get a clue on how to simplify math expressions

>>9878805
for example, if you're writing a gpu shader and you have sqrt(x)/sqrt(y), you'll get massively better performance if you write 1/sqrt(x*y) instead

>>9878816
but it is easier to manipulate expressions that don't have surds in the denominator

digital signal processing class or applied electromagnetics (RF and electromagnetic circuits, waveguides and optical fibers, antennas)course to round out my current schedule:
-senior design proj 1
-Photonics
-Labview
-Electrodynamics (quantum and non linear optics, computational EM, antenna and microwave engineering)

Plan to go to grad school and afterwards work in general field of optics, photonics, etc. im thinking DSP for more broad experience, but not sure

bump

What symbolic math package do you guys like? Maple? Mathematica? Im comfortable with Matlab from numerical stuff but their symbolic stuff seems a little lacking.

>>9879187
what have you tried?

>>9855388
test
[math] \partial [/math]

>>9856314
destroyed rubble doesn't dissappear or just all fly out the sides. Their animation isn't accurate.

>>9879582
>What symbolic math package do you guys like?
I'm not a "guy", but SageMath.

>>9855388
Assume $\sqrt{2}$ is rational, i.e. it can be expressed as a rational fraction of the form $\frac{b}{a}$, where $a$ and $b$ are two relatively prime integers. Now, since $\sqrt{2}=\frac{b}{a}$, we have $2=\frac{b^2}{a^2}$, or $b^2=2a^2$. Since $2a^2$ is even, $b^2$ must be even, and since $b^2$ is even, so is $b$. Let $b=2c$. We have $4c^2=2a^2$ and thus $a^2=2c^2$. Since $2c^2$ is even, $a^2$ is even, and since $a^2$ is even, so is a. However, two even numbers cannot be relatively prime, so $\sqrt{2}$ cannot be expressed as a rational fraction; hence $\sqrt{2}$ is irrational.

If $b=2c$ Why does $4c^2=2a^2$ and not $2c^2=2a^2$

>>9879740
Guys means people, fuckhead.

>>9879987
>If $b=2c$ Why does $4c^2=2a^2$ and not $2c^2=2a^2$
If b^2=2a^2 and b=2c then (2c)^2=2a^2, i.e. 4c^2=2a^2

>>9880126
Thanks. What’s the rule. Order of operations?

>>9880138
(xy)^n = x^n * y^n

>>9880031
That thing isn't a person.

>>9879740
>I'm not a "guy"
fascinating

a+b=ab
ab-a-b=0
Up to this point it's all fine
ab-a-b+1=1
Yeh, seems a bit random, but I follow
(a-1)(b-1)=1
I do not understand this step at all. How does this happen?
And supposedly this proves that a and b can't be 0 and 0, but must be 2, 2 - which, again, I don't understand.

please help

>>9880705
a+b does not equal ab dude
wat

>>9880791
>>9880705

Wait nvm, you're defining a + b = ab

>>9880705
(a-1)(b-1)=ab-a-b+1
a and b can be 0 and 0, you're probably missing something

ab-a-b+1=b(a-1)-a+1=b(a-1)-1(a-1)=(b-1)(a-1)

Are Anki cards still the best method for learning anatomy? It served me well last semester but I hear some people look down on it for some reason.

I finished my undergrad with a GPA of 3.2.
Is that bad?

>>9881334
Did you go to MIT?

Why is the fundamental group of a circle an abelian group? What theorem or result dictates this?

how do I prove if AxC=BxC and C is not the null set then A=B?

>>9881694
>>9881694
>why
because there are only 2 possible loops in the circle. One that does nothing, and one that goes around (or goes around the opposite way, but that's its group-theoretic inverse). Since there is only one generator, and any element commutes with itself trivially (due to associativity), then necessarily the group is abelian
>what theorem or result
well, the most definitive result says that its fundamental group is [math]\mathbb Z[/math], so it's not just 'any' abelian group.

Actually, you can show that a bouquet of n circles has the fundamental group of the free group on n variables, and it just so happens that the only abelian free group is the case n=1.

>>9881860
Choose an element c of C. Then AxC = BxC implies that Ax{c}=Bx{c}. But the latter are each bijective onto A and B respectively.

>>9881860
>how do I prove that A=B?
Let [math] a \in A [/math] bla... bla... bla... therefore [math] b \in B [/math] .
And vice versa.

Let [math] a \in A [/math] . C is not empty, so we can consider some [math] c \in C [/math] . We have that [math] (a,c) \in A \times C=B \times C [/math], so [math] (a,c) \in B \times C [/math] which means that [math] (a,c)=(b,c) [/math] for some [math] b \in B [/math], which implies that [math] a=b\in B [/math] .

>>9856594

Because it's colder than the side that's lit by the Sun.

>>9860964

Because most people who regularly use 4chan, including myself, have crippling insecurities, anxiety, depression, etc. This causes them to try to compensate for their own lack of social abilities or general success in life by inflating what they think they can do well, and putting down others who they believe aren't as good as them. It's literally just bullying, why do you think the word "Brainlet" is thrown around so often here? It's all that some people have- Some science/math ability, and they use that as an excuse to validate their own beliefs and cover up insecurities.

Intelligent people with no insecurities don't mistreat others or act pretentious.

>>9864866

Experience dealing with different functions and how you can configure them is the best way. Like most things in math, experience and practice trumps everything else. You just gotta toy with expressions and see how you can represent them in different forms while still keeping it the same expression. Just maybe find some practice problems online or something, or if you have an algebra textbook lying around try working out of that!

I'm studying some linear algebra on my own so I don't get my ass kicked as hard in the fall.
Is this the right way of taking the derivative of the l-2 norm of a vector?

I have a non-rigorous understanding of calculus. should I go with spivak, apostol, or just dive right into Real analysis?

>>9882812
real analysis
read the books if you want more info, and don't listen to the insufferable spergs who will insist that you have to read them. Good idea to have them on hand for reference though

>>9882812

What do you mean by
>non-rigorous understanding of calculus?

I would think a rigorous understanding of calculus is real analysis, so non-rigorous calculus could for me mean anything from knowing advanced high school stuff to a light calculus course with focus on the most elementary,rote methods and no focus on proof at all.

>>9882568
Why are you putting unnecessary parentheses and multiplication dots?
And, yes it is correct, but the gradient can be rewritten as [math] \frac{x}{\lVert x \rVert} [/math]

>>9882812
Apostol is great but it would take too much time to go through it then a real analysis book. Probably you should just do RA and complement with Apostol when you need it.

>>9883123
>Why are you putting unnecessary parentheses and multiplication dots?

I like
[math]
(x_i)^2
[/math]

More than
[math]
x_i^2
[math]

It's pretty much a purely aesthetic reason.

If precision measuring tools need to be calibrated periodically to ensure accuracy, then who calibrates the calibrators?

It shouldn't be physically possible for the calibrating equipment to be perfect and infallible 24/7, so who calibrates them?

>>9883634
Anyone?

I'm looking for some good practice/resources for converting metric units to imperial units quickly in my head. Preferably for pressure, temperature and distance. If anyone had any suggestions for that I would appreciate it.

>>9883636
that is literally a prototypical geometric series, just apply the formula

>>9884021
I vaguely recall some mnemonics they taught us in elementary school for this. Kinda useless in the age of portable internet (Google will auto-convert of you enter X <metric_type> to <standard_unit>), but, these might help:

https://study.com/academy/lesson/how-to-convert-standard-units-of-measure.html

https://www.wikihow.com/Convert-Within-Metric-Measurements

King Henry Doesn't Usually Drink Chocolate Milk rings a bell.

Page 10 and past the bump limit, seems we're overdue for a new /sqt/ though I canna think of a stupid question to start it off with myself.

>>9884143
ask what's a stupid question to ask