/sci/ - Science & Math

how can i proof that
−a = (−1) · a
on a "normal" field. only the standard definitions of a field are allowed

>>10081735
show that both values are additive inverses of [math]a[/math], and since the additive inverse is unique (proof: think), you can conclude the result.

>>10081737
>>10081735
yea i just got my head around that, still thanks mate

Trying to find all of the elements of [math]\mathbb{Z}_{45}[/math] with order 15. We know that [math]|\mathbb{Z}_{45}| = 45[/math]. Write [math]\gcd(m,45)=d[/math]. We need to find [math]m[/math] such that [math]O(x^{m}) = \frac{n}{d} = 15 \implies \frac{45}{15}=d \implies d=3[/math]. Thus, [math]\gcd(m,45)=3 \implies m=3[/math]. So [math]O(x^{3})=\frac{45}{3}=15[/math]. I'm thinking that's all there is. Is this reasoning correct?

>>10081783
Likewise in a cyclic group of order 24, all the elements of order 4 would be [math]x^{6}[/math] and [math]x^{18}[/math]?

>>10081783
It's correct except for the last part. m = 3 is not the only solution. Hint: m = 3*1, 3*2, 3*4, 3*7, etc, are all solutions.

>>10081872
Right, got it. Thanks.

>>10081859
If x has order 24, yeah.

good intro book for tensors, tensor algebra, etc. (maybe even some application)?

>>10081912
https://www.amazon.com/Tensor-Analysis-Manifolds-Dover-Mathematics/dp/0486640396
https://www.amazon.com/Tensors-Differential-Variational-Principles-Mathematics/dp/0486658406/
https://www.amazon.com/Vector-Tensor-Analysis-Applications-Mathematics/dp/0486638332
https://www.amazon.com/Elements-Tensor-Calculus-Dover-Mathematics/dp/0486805174/
https://www.amazon.com/Vector-Tensor-Analysis-Dover-Mathematics/dp/0486601099
https://www.amazon.com/Applications-Tensor-Analysis-Dover-Mathematics/dp/0486603733
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050175884.pdf

What would be better: going to a well known college with majors kind of related to your interest, or going to an okay college that has your major of interest?

>>10082171
depends on whether or not you plan on working in academia
if so, yes it matters what school you go to, if not, it doesn't matter nearly as much

>>10081732
I'll ask my question just once more:
Is there an alternative (better) definition for (the limit to) infinity than the "for all ε > 0" definition? This really just turns the concept of "infinitely great" into "infinitely close" i.e. the continuity of the reals, which sounds like circular reasoning to me since the set of real numbers is probably constructed using the concept of infinity, or limits thereto.

>>10082265
It's not at all dealing with "infinitely close" quantities. Read about the Archimedean principle.

>>10082283
property*

>>10082265
Option one: if you look up Dedekind's construction of the reals, you can modify the definition of cut a bit so that positive infinite is the set of Rationals, and minus infinite is the empty set.
Option 2: the limit to infinity of f(x) is the limit of 1/f(x) to zero from the right.

I know it's a dumb question i should have worked out in first year but if I have 2 graphs, 4 line plots on each how do I compare them besides just saying one line plot has a generally higher magnitude than another?

>>10082289
what

>>10082289
You want to try asking that again anon?

>>10082171
What you like doesn’t matter as much as who you know.

>>10082288
f(1/x)

>>10082283
>>10082288
Thanks. I got a little bit more feeling for it now. But I do still have trouble seeing the merit of the difference between "infinitely close" and "arbitrarily close". It does seem to work, of course.

Feel free to insult me.
I'm mildly certain I have Gonorrhea. I wan't to get diagnosed and prescribed medication without my parents finding out, since I'm still on their insurance.
I have an insurance card and a means of paying whatever additional fee there is.
What do I do? It should be said I'm over 18.

>>10082988

>For book recommendations, check the sticky and/or the /sci/ wiki
What is sticky ?

What keeps earth from crashing into the sun? If the suns gravity is attracting us, there should be some kind of force that pushes back to keep us in orbit, right? Where is this force coming frome?
Please explain in brainlet terms.

Could use some help wrapping my head around how light hits a sphere.

If the Earth's 23.5 degree axial tilt means that the angle at which the sun hits any given spot on the planet will change by +/-23.5 degrees relative to the equinoxes throughout the year, shouldn't the length of day in Los Angeles (34 degrees north) on winter solstice be the same as the length of day in Gothenburg (57.5 degrees north) on the equinoxes?

Los Angeles is literally in the same spot relative to the sun on December 21 as Gothenburg was on September 22. For this reason, Los Angeles and Gothenburg both have an apparent solar altitude of 33 degrees on September 22 and December 21 respectively. What I can't figure out is why the length of day is not the same as well.

Let a, b, c be integers. It is known that a|b and a|(b^2-c). How do I go about proving that a|c is also true? I think this is somehow done by using rules of divisibility, but cannot exactly figure out how.

What do I need to study to be able to read *this*

If I have something like [math]z = 3x + 5y[/math], then [math]{∂z} over {∂x} = 3 + 5y[/math] and [math]{∂z} over {∂y} = 3x + 5[/math].
But can I say that [math]{∂z} over {∂x + ∂y} = 8[/math]?

If I have something lime [math]z = 3x + 5y[/math], then [math]\frac{∂z}{∂x} = 3[/math] and [math]\frac{∂z}{∂y} = 5[/math]
But can I say that [math]\frac{∂z}{∂x + ∂y} = 8[/math]?

>>10083092
trigononetry and calculus, familiarize yourself with exponentiation if you haven't already
for the [math]sum[/math] and [math]prod[/math], see https://math.illinoisstate.edu/day/courses/old/305/contentsummationnotation.html

>>10083092
trigononetry and calculus, familiarize yourself with exponentiation if you haven't already
for the [math]sum_m^n[/math] and [math]prod_m^n[/math], see https://math.illinoisstate.edu/day/courses/old/305/contentsummationnotation.html

>>10083113
It's been a while since I finished college, is this good book to re-teach me Calculus? Would you recommend some specific book?

>>10083044
Why would you expect them to be the same? The only thing the two cases have in common is that the sun will be 33 degrees above the horizon at midday.

The two cases have identical solar elevations at specific points in time (solar noon on specific dates), but the axes are different so they'll follow different paths throughout the day (both circles, but with different radii and orientations).

Consider the situation of points just above and below the Arctic circle. A point just above will get 24 hours of sunlight on the solstice, a point just below will get the same solar elevation just before and just after the solstice, but will never get 24 hours of sunlight.

>>10083114
I wouldn't recommend any book to be honest, this https://www.youtube.com/playlist?list=PLZHQObOWTQDMsr9K-rj53DwVRMYO3t5Yr did the trick for me.
For exercises, just google for it, you'll find stuff like this: http://www.math.mcgill.ca/rags/JAC/dobson/dobson.html

>>10083119
Thank you for the video series link.

If 13% of my green apples are rotten, and 6% of my green apples are rotten, how many % of my total apples are rotten?

>plz halp

>>10083101
Weird notation, but since the function's linear, yeah.
>>10083129
Not enough information.

>>10083129
*6% of my red apples
sry

>>10083132
sorry I made a typo,
could you look at it again?

>>10083138
>>10083129
Nigga how many apples are there of each colour? Your answer varies depending on that.

>>10083132
How would you write it, generally? I mean the derivative of something with respect to multiple variables.

https://archive.org/details/TheWorldIsBuiltOnProbability/page/n7

Is this a good book to read about probability?

How do I write this equation in index notation?

[eqn] \vec{F} = \iint \vec{\vec{\sigma}} \cdot \mathrm{d}\vec{A} [/eqn]

Where [math]\vec{\vec{\sigma}}[/math] is the tension tensor in [math]\mathbb{R}^2[/math].

I've tried multiple things but with little success. I know the area differential is [math]d\vec{A} \equiv \epsilon_{ijk}\mathrm{d}x_i\mathrm{d}x_j \hat{e}_k [/math], but no matter how I put the equation together, I either get a scalar out of the tensor (which makes no sense since I'm interested in the tensions that are in the same direction as the area), or I get components of the tension that I don't want. I was looking for a nice looking equation like this:

[eqn] F_i = \iint \sigma_{ij}\epsilon_{jkl} \mathrm{d}x_k \mathrm{d}x_l [/eqn]

Does this equation not have a nice looking form in index notation?

>>10083101
Absolutely not.
[eqn]\frac{\partial z}{\partial x} = 3 \\ \frac{\partial z}{\partial y} = 5 \\
\frac{\partial z}{\partial x} + \frac{\partial z}{\partial y} = 8\\
\frac{\partial z \partial y + \partial z \partial x}{\partial x \partial y} = 8
[/eqn]
Which I don't know why you would want to do, but it is absolutely different than what you wrote.

>>10081732
Determine optimal gas for every loop of moded rankine with heatpump to extract heat from air.

>>10082999
first icon in
>>>/sci/catalog

>>10083176
Thanks, yeah, I guess that makes more sense.
I just started multivaribale calculus, I somehow got this idea that there has to be a derivative with respect to more than one variable.

>>10081732
How the hell do I prove that 650^(1/7) is irrational? I tried proving it like u would prove 2^0.5 is irrational but im stuck

>>10082265
i want to understand this post.

please point me in the direction to begin my quest

this is not a troll post, im just high as fuck

>>10083186
>I somehow got this idea that there has to be a derivative with respect to more than one variable.
There are. They are typically used in second order pdes, and there are quite a few of those, although the common ones usually involves the laplacian [math]\nabla^2 =\sum_i \frac{\partial^2}{\partial x_i^2} [/math], so they are usually separate, but some involve partials in different dimensions simultaneously, general relativity comes to mind.

Is {x|x^2 -9 >0} //intersection// Z an infinite set ? Is it bounded? Thanks

>>10083197
Assume it is rational. Then there is a fraction (a/b)^7=(n650/n) for some integer n.

>>10083211
I did that and i still dont see it maybe im a brainlet but could you elaborate more mate

>>10083144
I don't have that information. I just need the percentage. Oh my. I already expected it to turn out more difficult than imagined. Only thing I know for sure is that there are about 10 times more green apples than red apples.

does the dna get mixed during fertilization? if i'm a male, and i have some of my maternal grandfather's physical characteristics, does that mean i have no genetic connection to my maternal grandmother?

>>10083293
no, it gets mixed. genetic information sometimes jumps from one chromosome to the sister chromosome or another even chromosome. this is rare. however, much less rare and most importantly, during female meiosis, when the future mother prepares her egg cells, a process called 'crossing over' mixes everything up between maternal and paternal chromosomes.

>>10083226
If (a/b)^7=(n650/n), then b^7=n. Replacing: (a/b)^7=(650b^7/b^7). So: a^7=650b^7, for some a and b.

>>10083298
thanks friend

>>10083202
You should learn the definition of the limit, analysis 101.
This should help you: http://tutorial.math.lamar.edu/Classes/CalcI/DefnOfLimit.aspx

>>10083157
>I was looking for a nice looking equation like this:
But this is exactly what you get? Where's the problem?

>>10083066
if a divides b, then a divides b^2. If a divides b^2-c and b^2, then a divides b^2-c - b^2 = -c. If a divides -c, then a divides c.

Can someone help me with the problem in the picture? I'm fucking awful with these kind of questions

>>10083472
>definition of a factorial

>>10083472
>Can someone help me with the problem in the picture?
What have you tried?

>>10083472
Think about it longer than two seconds. It's obvious.

>>10083482
>>10083378
Idk if this is right but in any case I'm stuck

>>10083497
Fucked up the picture

>>10083114
Depends on what you want to get out of learning calculus. My general triad of recommendations is Calculus Made Easy (1910, available from Gutenberg), Apostol's Calculus Vol I, and Spivak.

>>10083197
> How the hell do I prove that 650^(1/7) is irrational?
It depends what axioms you can use. By the rational root theorem, the nth root of an integer is either an integer or irrational. But that would make the problem trivial, so I'm assuming you can't just assert the rational root theorem.

> I tried proving it like u would prove 2^0.5 is irrational but im stuck
Well, you can do it like that. The key point is that x^k≡x (mod n) for all x, for all positive k, n. If you expand x^k=(a*n+b)^k, all terms except b^k include a power of a*n and thus are multiples of n for any a,b. So it's the same as for √2 except you're showing that the numerator and denominator are both multiples of 650 rather than multiples of 2.

>>10083585
>The key point is that x^k≡x (mod n) for all x, for all positive k, n.
[citation needed]

>when nobody can solve your stupid question

>>10083585
>x^k≡x (mod n) for all x, for all positive k, n
you sure about that

>>10081732
I'm trying to do extra credit for my proof-based math class and need to prove you can create a bijection from [0,1] to (0,1)

I think my function works well enough, but I have no idea how to prove f is injective or surjective (gray text is what I've written up so far).

>>10083623
delete all the pointless fluff

>>10083618

is it about 12 per cent?

>>10083623
Map the irrationals to the irrationals, 1 to 1/2, 0 to 1/3, 1/2 to 2/3, etc. In other words, set the ennumeration of the rationals to the ennumeration of the rationals.

>>10083129
13%X+6%Y=n%(X+Y)

>>10083289
>about
if it's exact, then
13%(10Y)+6%(Y)=n%(11Y)
Y(10*13%+6%)/11y = n%
(10*.13+.06)/11=n%
n=12.36%

>>10083551
Learn. I'll grab the Spivak from the Google.

>>10083623
If your function is a pain to prove, make a better function. Also, brevity is nice.

>>10083632
Like this.

>>10083632
>>10083644
Your function makes sense, but how is it any different from mine?
In both cases we're sort of "linking" numbers in our domain to numbers in our codomain.
Is there a reason why we used "1/3", because we could also map 1 to 1/2, 1/2 to 1/4, ...
And we could map 0 to 1/3, 1/3 to 1/9, ...

Would that make it easier to prove?

>>10081732
Hoe dew I dew te meth?

>>10083644
Got back with more brevity. f: [0, 1]->(0, 1).Map the irrationals to the irrationals. f(n/m)=(n+1)/(m+2).
>>10083653
You literally don't have to prove anything with that one.

>>10083667
Forgot to say that every rational has to be in the relatively prime form for that one, sorry.

>>10083667
Or at least, what would I need to write down?
I made the function a lot more readable, but I still don't know how to show (or even if I need to) f is bijective.

>>10083653
Having 0 and 1 go to the same sequence is easier because then you have to prove stuff for one sequence instead of two. If you do two sequences, you also have to show that they are mutually exclusive.
The easiest sequence to use in my personal opinion is 1/2, 1/3, 1/4, ..., but as I said, as long as you can prove it's countable and infinite you should be fine.
Surjective is easy, just consider when the output is and isn't decided by the sequence thing.
Injective is easy, just consider when the output is and isn't decided by the sequence thing.

>>10083667
>not even a function
Nice.

>>10083686
I think I've got where you're coming from.
If x can be written as (1/2)^n, for some integer n>0, x belongs to the set S.
If x can be written as (1/2)^n, for some integer n>0, x belongs to the set T.
We define f:[0, 1]->(0, 1) as
f(0)=1/2
f(1)=1/3
for s belonging to S, f(s)=s/2
for t belonging to T, f(t)=t/3
Else, f(x)=x
But this is clunky as shit.

>>10083686
let f(x) = b
case 0: b in S. Then x = 2b
case 1: b in T. Then x=3b if b != 1/3, otherwise 0
case 2: literally everything else. x = b

You also need to state that S and T have nothing in common to prove that f is a function.

>>10083727
Thank you so much! I think I know what to do now!

>>10083703
When you say 0 and 1 go to the same sequence, what sequence would that be? I'm looking atwhat you wrote here:
>>10083632
[math]
0 \rightarrow 1/2
1 \rightarrow 1/3
1/2 \rightarrow 2/3
[\math]
But I for 1/3, wouldn't your function lead to 2/4 (which is already covered by 0 -> 1/2? )

>>10083744
Google "ennumerate the reals".

>>10083744

Quoting two different anons in the second part, but basically for whatever sequence S you're using,
0 -> S_0
1 -> S_1
S_n -> S_(n+2)

Might be a brainlet on how perturbations work, so I'm gonna start with some stuff in class that apparently went over my head, since my notes now look like Chinese or something.

Consider the ODE [math]y' = y + x[/math]. By assuming small x, show that the right combination of terms results in [math] y \approx \frac{x^2}{2!} + \frac{x^2}{3!} [/math], which is a Taylor series expansion of the exact solution [math] y = e^x - x - 1 [/math].

The actual homework problem is to perform a similar analysis assuming large x instead of small, but I think I'm missing some of the steps to get to that point. I think there's some game I'm missing from my notes to get to these points, but fuck me if I know what. Any ideas, /sci/?

cellular biology.
what the fuck is this supposed to represent?

>>10083380
The problem is I get this:
[eqn] F_1 = \iint \sum_{jkl} \sigma_{1j}\epsilon_{jkl}\mathrm{d}x_k\mathrm{d}x_l \\
F_1 = \iint\left[\left( \sigma_{11}\mathrm{d}x_2\mathrm{d}x_3 - \sigma_{11}\mathrm{d}x_3\mathrm{d}x_2\right) +\\
\quad\quad\quad + \left(\sigma_{12}\mathrm{d}x_1\mathrm{d}x_3 - \sigma_{12}\mathrm{d}x_3\mathrm{d}x_1\right) + \\
\quad\quad\quad + \left(\sigma_{13}\mathrm{d}x_1\mathrm{d}x_2 - \sigma_{13}\mathrm{d}x_3\mathrm{d}x_1\right)\right]
[/eqn]
Which is obviously incorrect, since 1: it's taking into consideration shear stresses [math]\sigma_{12}, \sigma{13}[/math], and 2: each parcel would be zero since [math]\mathrm{d}x_i\mathrm{d}x_j = \mathrm{d}x_j\mathrm{d}x_i[/math]. Perhaps if I square the Levi-Civita symbol and take half the value that would fix the second problem, but I am not sure about the first. Is it even a problem? Maybe the shear-stress are not taken into account depending on the integration limits and the surface boundaries? It would be then:
[eqn] F_i = \frac{1}{2}\iint \sigma_{ij}\epsilon_{jkl}^2\mathrm{d}x_k\mathrm{d}x_l [/eqn]

If breast milk contains immunoglobulin, doesn't that mean a child will end up healthier if they are breastfed by multiple different women?

I am having a test to determine my "psychology " for a scholarship soon and i am afraid of it. They told us that there would be trick questions and people with unstable/labile psyche won't make it. Can anyone give some advise or a link where i can train for something like that?

>>10083829
What you're doing is taking the cross product of a vector (dx,dy,dz) with itself. In other words, your surface isn't a surface. You have to parametrize it.

[math] \mathrm d \vec A = \vec n \mathrm dA = \left( \frac{ \part \vec R}{\part t} \times \frac{ \part \vec R}{\part s} \right)\mathrm dt \mathrm ds [/math]

For example if you plug in the xy-plane (x_1=t, x_2=s, x_3=0) you only get

[math] dA_3 = \epsilon_{312} \frac{ \part x_1}{\part t} \frac{ \part x_2}{\part s} \mathrm dt \mathrm ds = \mathrm dt \mathrm ds [/math]

>>10081732
Why are molecules structured like the way they are, and is it wrong to write them in a different order? Like for example, glucose is C6H12O6. Can't I draw it like C-C-C-C-C-C-H-H-H-H-H-H-H-H-H-H-H-H-O-O-O-O-O-O or is it a must that I do it pic-related?

>>10083829
What you're doing is taking the cross product of a vector (dx,dy,dz) with itself. In other words, your surface isn't a surface. You have to parametrize it.

[math] \mathrm d \vec A = \vec n \mathrm dA = \left( \frac{ \partial \vec R}{\partial t} \times \frac{ \partial \vec R}{\partial s} \right)\mathrm dt \mathrm ds [/math]

For example if you plug in the xy-plane (x_1=t, x_2=s, x_3=0) you only get

[math] dA_3 = \epsilon_{312} \frac{ \partial x_1}{\partial t} \frac{ \partial x_2}{\partial s} \mathrm dt \mathrm ds = \mathrm dt \mathrm ds [/math]

>>10083964
No, because the baby is only dependent on getting immunoglobulin from the mother for a little time till the baby can produce it itself.

>>10084000
Because organic chemistry can be a bitch, and a particular set of atoms in a molecule can represent a ton of different compounds. Look up Isomers. Just saying C6H12O6 is extremely ambiguous, for example you could also be referring Mannose, Galactose, Altrose, etc. They can even have quite different properties, so if you want to unambigously refer to a certain organic compound you need to give its structure.

It gets even more annoying with stereoisomeres, where the chains of atoms are always the same but the only difference is how some of them are oriented, so you also have to take care of orientation.

Since the derivative of log(z)/z = (1 - log(z))/z^2, is it correct to say that the complex derivative exists everywhere except for at z = 0?

This is on the principal branch of log (-pi, pi]. I'm not sure if the derivative exists when z is on that line (i.e., the real component of the log is negative and the imaginary component is 0).


Can someone correct me if I'm wrong?

>>10084005
Makes sense. I can see how after parameterizing the surface, only one of the components of the cross product would have a value (as long as you used a standard parameterization, of course), still the full equation doesn't come:
[eqn]F_i = \iint_S \sigma_{ij} \epsilon_{jkl} \frac{\partial S}{\partial x_k}\frac{\partial S}{\partial x_l}\mathrm{d}x_k\mathrm{d}x_l[/eqn]
You can see how the indices k and l have already been reduced with the partial derivatives. I don't know if this is allowed or not, maybe it is since they are integration variables and would disappear, but it's not as smooth, it feels like it's incomplete. Maybe it's something like this (I haven't done the algebra yet, but it looks better):
[eqn]F_i = \iint_S \sigma_{ij} \epsilon_{jkl} \frac{\partial S_k}{\partial x_m}\frac{\partial S_l}{\partial x_n}\mathrm{d}x_m\mathrm{d}x_n[/eqn]

Would taking up smoking for two weeks help my mental performance or could I get the same effect with more caffeine?

>>10084493
do both and exercise, cut out trash food, get cardio. also don’t smoke just buy a vape

Does anyone know of decent sources for data concerning graduate school admission statistics?
This sort of stuff seems to be very easily available for undergrad but it's very difficult to find grad stats for some reason.

>>10084496
>get cardio
True dat. Didn't run for a month and felt like shit, recently took up distance running again and it's like crack. Could I use low strength nicotine gum instead of smokes though? Don't wanna vape for obvious reasons.

>>10083114
https://www.amazon.com/Methods-Mathematics-Calculus-Probability-Statistics/dp/0486439453
https://www.amazon.com/Elementary-Calculus-Infinitesimal-Approach-Mathematics/dp/0486484521

>>10083623
>I'm trying to do extra credit for my proof-based math class and need to prove you can create a bijection from [0,1] to (0,1)
How the fuck is that extra credit? Is this an intro to proofs for brainlet cs major class?

>first white paragraph
Why so many words? Have you never taken calculus?

>2 shifts
Just map 1/n to 1/(n+2) and 0 to 1/2.

>>10081732
How would /sci/ do this >>>/g/68145419

youtube.com/watch?v=S2rECJOfokg&t=82s youtube.com/watch?v=S2rECJOfokg&t=82s youtube.com/watch?v=S2rECJOfokg&t=82s youtube.com/watch?v=S2rECJOfokg&t=82s youtube.com/watch?v=S2rECJOfokg&t=82s

>>10082882
Because the definition of the epsilon/delta says it will go on like that forever, so you can kind of stop at an arbitrary spot that isn’t infinite. It’s not that you can’t think of them as infinitesimals, it’s just that standard analysis avoids doing so.

>>10083042
The “sideways” speed of the earth is just enough to keep us going in a circle, “falling” around the sun but at the same time not shooting off into space.

>>10083623
Map zero and one to infinities.

[math] \underset{\underset{\underset{\underset{\underset{\underset{\underset{\blacktriangle\blacktriangle}{\blacktriangle}\underset{\blacktriangle\blacktriangle}{\vartriangle}\underset{\blacktriangle\blacktriangle}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}\blacktriangle}{\blacktriangle}\underset{\blacktriangle\blacktriangle}{\vartriangle}\underset{\blacktriangle\underset{\underset{\underset{\blacktriangle\blacktriangle}{\blacktriangle}\underset{\blacktriangle\blacktriangle}{\vartriangle}\underset{\blacktriangle\blacktriangle}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}\blacktriangle}{\blacktriangle}\underset{\blacktriangle\blacktriangle}{\vartriangle}\underset{\blacktriangle\underset{\underset{\underset{\underset{\underset{\underset{\blacktriangle\blacktriangle}{\blacktriangle}\underset{\blacktriangle\blacktriangle}{\vartriangle}\underset{\blacktriangle\blacktriangle}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}\blacktriangle}{\blacktriangle}\underset{\blacktriangle\blacktriangle}{\vartriangle}\underset{\blacktriangle\underset{\underset{\underset{\blacktriangle\blacktriangle}{\blacktriangle}\underset{\blacktriangle\blacktriangle}{\vartriangle}\underset{\blacktriangle\blacktriangle}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}}{\blacktriangle} [/math]

[math] \underset{\underset{\underset{\underset{\underset{\underset{\underset{\blacktriangle\blacktriangle}{\blacktriangle}\underset{\blacktriangle\blacktriangle}{\vartriangle}\underset{\blacktriangle\blacktriangle}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}\blacktriangle}{\blacktriangle}\underset{\blacktriangle\blacktriangle}{\vartriangle}\underset{\blacktriangle\underset{\underset{\underset{\blacktriangle\blacktriangle}{\blacktriangle}\underset{\blacktriangle\blacktriangle}{\vartriangle}\underset{\blacktriangle\blacktriangle}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}\blacktriangle}{\blacktriangle}\underset{\blacktriangle\blacktriangle}{\vartriangle}\underset{\blacktriangle\underset{\underset{\underset{\underset{\underset{\underset{\blacktriangle\blacktriangle}{\blacktriangle}\underset{\blacktriangle\blacktriangle}{\vartriangle}\underset{\blacktriangle\blacktriangle}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}\blacktriangle}{\blacktriangle}\underset{\blacktriangle\blacktriangle}{\vartriangle}\underset{\blacktriangle\underset{\underset{\underset{\blacktriangle\blacktriangle}{\blacktriangle}\underset{\blacktriangle\blacktriangle}{\vartriangle}\underset{\blacktriangle\blacktriangle}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}}{\blacktriangle}}{\blacktriangle} [/math]

>>10084848
>>10084850
yeah i don't have an answer to this one

Anyone else have ADHD? I am undiagnosed and have an appointment soon, but from reading online about symptoms and other people's experiences, I am fairly certain I have it.
I am at a top uni, 3rd semester, but I am getting cucked so hard. Last year I chalked it up to the difference in high school and college, it was a huge jump, and this year I started out so motivated but it all fell apart after 3 weeks because I just can't manage time.
I am going to see a school doctor about it, but I was wondering if anyone else has experience with it. Does the medication actually make it better? I have around a B+ GPA, which is about the 15th percentile (among graduating seniors) here. Does anyone have advice for the interim before the appointment, which is muti-stepped and I won't be diagnosed for probably about another month?

>>10084882
>does the medication actually make it better
absolutely

>>10084826
Okay, all of that makes sense. "[T]he definition of epsilon/delta" implies the definition of the "greater than" sign, which implies the continuity of the reals. And this is not circular reasoning since the reals can be constructed completely independently from the concept of the limit. Still, won't you need a set-theoretical axiom of infinity somewhere? Forget limits, I'm looking for the exact origin of infinity in mathematics.

>>10084907
>[T]he
didn't really need to do that

>>10084907
Yes, there just so happens to be an axiom that's literally called Axiom of Infinity. Look up the Zermelo-Fraenkel set theory.

>>10084894
What's it like?

>>10084918
Thanks, very good to know.

>>10084916
lol

Need to remove one subject from this list

Which one and why

>>10084976
If undergrad, combinatorics
Y: undergrad level is watered down for brainlet cs major

>>10084978
it's a grad course in matroid theory but I have the option of taking it for my undergrad degree

Is there a way to get ethyl propanoate from 1-propanol and something else?

I thought etherification always went

R-CH2OH + R'-COOH -> R'-COO-R + H2O

>>10084979
So they're all grad level courses? What does Geometry cover?

>>10085005
Geometry and Combinatorics are grad courses

Pic related it's the description for the geometry course. Not really descriptive

>>10085033
The lecturer's profile seems to indicate that it's related to "finite projective geometry"

Is that basically algebraic geometry?

>>10081732

Brainlet here, is it possible for a genus 0 curve to have zeros as in pic attached (hyperbola with line in each quadrant of x,y axes)? Thx me brehs.

Does adding a divergent integral to a convergent integral yield a divergent integral?

>>10081732

wy won't scientists extract chloroplasts modify them and inject into deeper layers of human skin to make people feed off sunlight?

>>10084984

are you over 18?
its illegal to make alcohol if you're under 18 here

>>10084299
>I can see how after parameterizing the surface, only one of the components of the cross product would have a value
Not for arbitrary surfaces, only if it's a coordinate plane

My notation might've been a bit confusing, let me explain a bit more in depth. You can write the surface element as a unit normal vector times the area of the element

[eqn] \vec F = \iint \vec{\vec{\sigma}} \mathrm d\vec A = \iint \vec{\vec{\sigma}} \hat n \mathrm dA = \iint \vec{\vec \sigma} \frac{\vec n}{||\vec n||} \mathrm dA [/eqn]

When you parametrize things you get with [math] \mathrm dA = ||\vec n||\mathrm du \mathrm dv [/math]

[eqn] \iint \vec{\vec \sigma} \frac{\vec n}{||\vec n||} ||\vec n|| \mathrm du \mathrm dv = \iint \vec{\vec \sigma} \vec n \mathrm du \mathrm dv = \iint \vec{\vec \sigma} \left( \frac{\partial \vec r(u,v)}{\partial u} \times \frac{\partial \vec r(u,v)}{\partial v} \right) \mathrm du \mathrm dv [/eqn]

Where [math] \vec r(u,v) = (x(u,v),y(u,v), z(u,v)) [/math] is just a vector pointing to points on the surface. We use the cross product of two tangent vectors to get a normal vector.

In component form it's

[eqn] F_i =\iint \sigma_{ij} n_j \mathrm du \mathrm dv = \iint \sigma_{ij} \epsilon_{jkl} \frac{\partial x_k}{\partial u} \frac{\partial x_l}{\partial v} \mathrm du \mathrm dv [/eqn]

>>10084984
ethanol and propanoic acid

>>10085174
The sum of the integrals is the integral of the sum only if all integrals involved converge.

>>10081732
why do i fuck my PCR's everytime?

Why is this wrong?
Apparently A should be 8/27
B should be -46/27
and C should be 74/27

>>10085236
maybe you do not pipet precisely enough, maybe the primer sequences are shit, maybe the temperature is wrong, do you include a control that has worked before?

>>10085176
they need their own genetic information to work, also our immunosystem would kill them, and our cells would not know how to handle those extra sugars

>>10083964
>>10084032
I'd say yes, it would.

>>10084508
>Could I use low strength nicotine gum instead
I highly recommend you do that, or use nicotine patches

>>10081732
How can I make a virtual machine that is nearly impossible to be detected by any software?
>Plz gib (you)s

>>10085301
You need linear, not constant, numerators when the denominator is not of the form (x-a)^n.

>>10085301
It's not wrong, per se.

But you can factor 3x+9 as 3(x+3), and write the RHS as a/(x+3)+b/(x+3)^2+c/(x+3)^3, which will give you the coefficients which you're looking for (the ones with the /27).

So you might have misread the question, or the question might not have been written correctly.

>>10081732
Can someone explain why carburetor icing occurs? Is it because
>temperature drops along with static pressure in the venturi
or
>fuel evaporating causes a cooling effect
Or is it both?

>>10084984
Oxidize the 1-propanol to propanoic acid and make it react with ethanol.

>>10085174
Yes, ofcourse.

>>10085234
Not an answer to his question.

How Do I Show that a field with {0,1} as my only elements is really a field? Do I seriously need to try every condition with every possible combination in order to show that it really is one?

>>10085553
>How Do I Show that a field with {0,1} as my only elements is really a field?
Show that it satisfies the field axioms under whichever addition and multiplication operations you are using.

>>10085567
So I just "brute force" every possible combination like a retard? Hoped there would be a more elegant way

>>10085577
>So I just "brute force" every possible combination like a retard?
What do you mean?

>>10085577
>showing that the definition of what constitutes a field hold
>brute forcing all possible combinations
What did he mean by this?

>>10085336
>>>/g/

But by making it harder to do stuff like this
https://superuser.com/questions/1128339/how-can-i-detect-if-im-within-a-vm-or-not

>>10085590
for example Distribution:
(a + b) * c = a * c + b * c for all a,b,c in {0,1}
now I need to proof that this holds, so I have to show that every single combination of 0s and 1s are still equal on both sides?
Seems like 3 pages of 0s, 1s and a big load of dick to me, so I though there is a different method that doesnt involve listing every fucking combination up

>>10081732
I feel retarded. Can someone help me understand this one identity at the top of page 6. Specifically this:

[eqn]\frac{1}{a^{n+w}} = a^{-n}(1-w*ln(a))[/eqn]

http://eulerarchive.maa.org/docs/translations/E432en.pdf

It’s probably obvious where it comes from but I feel dense as a brick for not seeing it. I really want to get past this so I can read the rest of this paper.

Are any of you engineers? Can I "interview" (ask you to fill out an online questionnaire) for my class? Do you know anyone who might be able to help me out?

In order to graduate from college (as a math major...) I have to interview an engineer about their career. I have zero social skills and an empty resume so it's been impossible to find anyone locally to interview. The only requirement is that you are or were an engineer at some point and you can verify that you were.

My inability to remember small details over a long period of time is going to cause a lot of problems in my career I think. I can study a particular region of anatomy on anki for a few months, but once I stop I will be unable to remember shit within a month. Is this normal? For example I got a very good score on my physiology unit last semester, but right now I can't remember shit because I haven't needed to access or remember that information.

>>10085774
I mean, it's not like it's actually a true identity. It only "works" because w is an infinitesimal quantity (read page 5) that Euler is performing some voodoo with. w is basically 0.

Hello, you see during the Proof of Euclid's lemma, we use some propositions (the 19th, 20th, 21st, 29th): https://en.wikipedia.org/wiki/Euclid%27s_lemma#Proof_of_Elements
I wonder is those proposition or some of those are axioms.

The propositions are the following:

If a /b=c/d, then ad=bc; and conversely.

If a/b=c/d, and a, b are the least numbers among those that have the same ratio, then c=na, d=nb, where n is some integer.

If a/b=c/d, and a, b are prime to one another, then a, b are the least numbers among those that have the same ratio.

If a is prime and does not measure b, then a, b are prime to one another.

>>10081732
What do you do in this question? I don't get why I can't think of a solution. Like I've been studying this sort of stuff for what, 4-5 years now? This is the very, most absolute basic thing you can do and I can't do it, should fucking shoot myself God fucking damnit. I swear I am brain damaged but nope "got to be a good person :-)" in spite of being a retard has me doing this to try and be useful for the end of time most likely.

Like I rearrange σA = F then what? Tensile strength = Young's Modulus doesn't it? What the fuck is the elastic limit there for, we don't know if its going to Yield or fracture we just want the force so what the fuck do you do with it? Its obviously there for a reason. How great to think you're making progress in life when you might as well be a ten year old, I want to fucking scream.

>>10081732
Stupid question here. Let me just preface this with the fact that i am NOT anti-vaccination. I remember seeing someone post a link to an article that talked about how antigenic memory gained from vaccination can make vaccinated individuals more susceptible to viruses like the flu which frequently undergo antigenic drift.
The reasoning was that when your body is presented with a virus for which it has antigenic memory, it will produce the antibodies needed to fight that infection. However, when presented with a similar, but different strain of the same virus after antigenic drift has occurred, your body will produce the antibodies it has due to antigenic memory, rather than the antibodies needed to fight the new strain of the virus. This makes those who were vaccinated more susceptible to some strains that have undergone antigenic drift than those who were not vaccinated.

Does anyone know what article im talking about? Ive done endless amounts of googling, but alas, my google-fu is not strong enough.

>>10085802
Thank you anon, I get that w is approaching 0 and that, when it does, that “identity” is true but I don’t get where the natural log comes from. Why not Exp[a] instead. Why not Sin[a]. Where does he come up with the natural log. It’s bugging the hell out of me.

>>10085924
https://www.ncbi.nlm.nih.gov/pubmed/25589639
this one seems to cover the topic

>>10085978
Original antigenic sin! This is what i was looking for, i found it in the discussion of that study. Thank you anon.

So im working on this calc 2 problem. The initial question is "Find the area of the region that lise inside r = 3sin(theta) and outside of r = 2-sin(theta). These are polar coordinates. Ill post the graph in a second. Pic related is where Im at so far, but I realized that in step 5 I hit a problem. My first instinct was that I could pull out the 8/2 from the whole integral, but that seems like it would screw up the -4, since it is a different term. The first version of line 5 is what I am talking about. (the purple one) What I THINK I need to do is the second line 5, or the green one. I think I need to break the integral into two different integrals, and only pull the 8/2 out of the first one.

The first time I solved this problem, I got exactly twice the answer I should have gotten according to our class notes. (we solved this exact problem in class, but the proff didnt show any work, just the setup and final answer. She also didn't take advantage of the symmetry, so thats why I am integrating only to pi/2 instead of 5pi/6.


TLDR: In line 5, which version is correct, the green, or the purple?

Thanks a lot.

>>10085974
>Where does he come up with the natural log.
Taylor series expansion:
a^x =
sum x^k * log^k (a) / k!

if x is very small then x^k is very small, so the terms with x^k are treated as zero for k>1

>>10086009
Here is the graph.

>>10086009
Oh, sorry to spam the thread, but I should mention that our proff has been known to make occasional computation mistakes, so it IS possible that the answer should be what I got originally...

I failed my comp sci test but aced my calc3 test. Not failing the class, but it's brought that grade down quite a bit.
Think I could still get into a decent grad school? Would they even care?

From calculus 1 regarding the error for Simpson's Method and Trapezoid Method.

I'm given a function, its second and fourth derivative and their maximum points and an accuracy, and my task is to calculate the amount of intervals n such that the answer lies within the error.

So naturally I would think of the error formulas, as they are simple:
E = K(b-a)^3/12n^2 where K is the maximum value of the second derivative
E = K(b-a)^5/180n^4 where K is the maximum value of the fourth derivative

So, I've got the E, I can find K by finding the maximum value of the second and fourth derivative easily. I just put the numbers into the formula for error and solve for n. But I can't seem to get it right! I know for the Simpson's Rule, n has to be even and for trapezoid method n has to be a natural number. The maximums I have found are indeed within the range of the definite integral, so that's not it.

Any tips?

Will covering my entire body in talcum powder help me feel cool during the summer?

>>10086137
... maybe? I might also increase your risk for cancer. (talc apparently is a carcinogen. And to think all these years we've been rubbing it into our children's ass-holes...)

I would go with gold-bond powder. Especially the kind with the menthol in it. I dont think it will actually cool you off, but it will probably make it FEEL like you are cooler. Temperature wise I mean. If you walk around outside with goldbond covering your entire body, people will probably not go "oh man, look at that guy, he's really cool" except to make a pun. But dont let that discourage you. This is how science happens outside of the academic world, and some of the best things to happen to our species happened outside of academia.

>>10086141
>talc apparently is a carcinogen
Wasn't it just that one product from JNJ that had a byproduct which was carcenogenic?

>>10086141
They can't even find a definitive link between being a talc MINER and increased lung cancer. Not only that, but talcum powder is now filtered to remove the asbestos that naturally occurs in talc, an amount of asbestos that wasn't even enough to cause lung cancer in the miners.

>>10086148
>>10086145
oh, I did mot realize this. Thanks for the heads up.

By the way, what exactly IS asbestos anyway? I know it has insulation properties, and it is a carcinogen, but what is it really? like what does it look like? is it a fiber? where does it come from?

>>10086137
>Will covering my entire body in talcum powder help me feel cool during the summer?
Why don't you try it and find out?

>>10086168
It's not summer.

Is saying [math]x^{2}(y-z)=(z-y)[/math] enough to prove [math]y=z[/math]?

>>10086182
(for all x and some y,z)

anyone good in chimistery?

>>10086182
yes

>>10086151
It's a very fragile fiber, it's a carcinogen because inhaling it will cut up your lungs pretty bad

>>10086206
Ah, I see. Thanks.

>>10086182
>>10086191

Generally, no. For x != y:

[math]x^2(y-z)=(z-y) \Rightarrow x^2 = \frac{z-y}{y-z} = - \frac{z-y}{z-y} = -1 \Rightarrow x \in \{i, -i\}[/math]

>>10086136
bump

>>10086229
quoting from >>10086183
>for all x

>>10086236
>>10086136
> I can't seem to get it right
What's the problem exactly?

> The maximums I have found are indeed within the range of the definite integral, so that's not it.
What do you mean? What's the function? If you computed local maxima, did you check the values at the interval boundary?

>>10086252
Sorry, my english isn't that great. I'm looking for the least number of intervals n so that the error lies within a given number.

I figured it out, though. I miscalculated K, since I thought it would be the maximum value of the second derivative. K is supposed to be the absolute value of the maximum or minimum value of the second derivative, whichever is larger. I had -8 at a point in the interval, but used 2 instead since it was larger..

But the absolute value of -8 is indeed larger than 2.. so the total answer wound up being sqrt(4) as large as I had thought. Thanks for your reply anyway!

>>10086182
well, the case x=0 is enough to show y=z

>>10086032
Thank you. That makes perfect sense. I should have realized this sooner but it took me off guard how he straight up launched into it and didn’t describe what he was doing. Many thanks.

>>10086189
Is this a esterification? Add the motherfucking catalysts.
And by god, draw it on a paper and take a picture. this looks hideous

Can a mutation in a cell cause it to start producing viruses?

Are there any organisms that produce viruses without being a "host" for the virus? Does that even make sense, definition-wise?

>>10086189
>aqua phase
>acetat ethyl
>those drawings
>chimistery
anon what the fuck, I want to help but this has to be a joke

How do I find the determinant of this matrix using Laplace expansion?

Matrix:
2 1 0
3 4 0
0 0 2

I know the determinant is 10
I'm not sure if my understanding is correct.
Here's what I did to get the determinant
Choose a cofactor:
I chose C33, C33 = -1^(3+3) = 1
Choose a minor:
I chose M33, M33 = 0 + 0 + 2 + 0 + 0

Multiply the minor by the cofactor:
1*2=2
Find the determinant of the new sub Matrix 33:
2 1
3 4
(2*4)-(3*1)=5
Multiply the determinant by the product:
2*5 = 10

Have I done this correctly?

>>10086398
I don't think so. The closest thing to that phenomena would be prions.

>>10086426

Which math fields have the most obtuse, retarded and confusing notation?

If a machine were made that could account for the location, trajectory, and energy within every atom in our universe, would that machine be able to accurately predict the future? Could a person who read the machine's prediction act against the prediction or would the machine's readouts be completely deterministic and inevitable regardless whether or not someone had read from it?

>>10086530
to an extent yes
you won't be able to track every single atom inside a star, but you'd be able to predict anything that would matter

>>10086451
>Which math fields have the most obtuse, retarded and confusing notation?
IUTeich

>>10086530
The machine's prediction becomes outdated the moment it shows it to anybody.

>>10085804
Those are all theorems and can be shown from Peano's axioms abd the definitions.
>>10086451
Statistics is physical pain tier. Hypothesis testing is cancer.
Graphs is "shit but it has to be shit".

>>10085882
it's not 98.1N?

https://marketing-insider.eu/buyer-black-box/

Is it acceptable to use buyer's black box as a theoretical framework in a thesis

>>10086009
i got the same final answer, but only the green line is correct. in the pink version you should have -1 at the end, instead of -4.

>>10086594
It is, I realised a few hours ago after taking a break that half the question was redundant and you only had to multiply mass and gravity. I can't believe that tripped me.

I hate discrete maths infinite new notation so fucking much. Urgh

>>10086677
haha thank god for that. I thought I was going insane wondering where the additional force was coming from. glad you got it. sometimes it takes a break for it to click.

Any help with this exercise?

>>10086855
I don't know any physics. From glancing at the wiki a wave function has an associated probability density. As such the wiki mentions the required normalization property in this section https://en.wikipedia.org/wiki/Wave_function#Position-space_wave_functions..

I'd start there to find A.

>>10086855
1. are you retarded? A=[math]\sqrt{6}[/math]
2. uniform
3. 1 - triangle y=x from 0 to 2 = 1-1/2*2*2*1/6 = 2/3

What are the best introductory books on information theory and cybernetics?

How the fuck do I study facts and stuff without Anki? Just write the same sentence over and over? It's a hard unit where I have to translate written textbooks into actual physical movement for a practical exam.

HALP

>>10086398
>Can a mutation in a cell cause it to start producing viruses?
yes but only if that cell is already infected by that virus and virus production is currently somehow inhibited by a cellular mechanism, read about apobec deaminases
>Are there any organisms that produce viruses without being a "host" for the virus?
human researchers are the only organisms I guess. however there are some insects that have worm-like parasites that have viral infections that can become beneficial for the insect.
>Does that even make sense, definition-wise?
not very much

If light is always touching you (because we're rarely in total darkness), why can't you ever feel it?

>>10087156
it's too


light

can someone explain to me what i'm doing wrong in matlab? i want to express this but

>>10087234
this is what I get in matlab by using

x = linspace (-5,5,100);

for k = 1: length(x)
if (abs(x(k)) >= 0.5 && abs(x(k))<= 1.5)
y(k) = 1/6*(5-3*(abs(x(k))-sqrt(-3*(1-abs(x(k))).^2 + 1)));
elseif (abs(x(k)) <= 0.5)
y(k) = 1/3*(1 + sqrt(-3*(x(k))^2+1));
else
y(k)=0;
end
end

plot (x,y)

How do you read this sign: [=] ?

>>10087294
It's an equivalence relation, like [eqn]\equiv[/eqn] but it could be any equivalence relation not just modulo.

I took a course in college that was pretty fun and was wondering if there were any work books on it. it was an intro to logic class we used modus penens, modus tollens, etc. It was basically all word problems you had to break down into logical proofs and then check the validity. Are there any work books like that? It seems like it would be a good pass time when I'm bored to work through some of those.

>>10081732
In the Lorentz factor (for time in this case):
[math]{\displaystyle \Delta t'={\frac {\Delta t}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}}[/math]
I see that it accounts for instantaneous relative velocity. As far as I know, time dilation is reciprocal for two non-accelerating bodies (let's ignore gravitational fields for practicality), and the "time travel" happens during acceleration.
In the typical meme twin "paradox" (not a paradox) experiment, how would you calculate the total time "travelled"?
Is the acceleration irrelevant? As in, doesn't it matter how fast that relative velocity is achieved (and reversed)?

>>10087301
Thank you

I don't understand how Newton's first law can apply to moving objects
Obviously if an object is motionless then the sum of the forces that act upon it is zero, but why is the sum still zero if the object is in linear motion?

>>10087385
Read the second law fifty times until you get it.

>>10087389
Because in the case of linear motion, acceleration being null, mass times acceleration gives the null vector?
Fuck I'm retarded.

>>10085464
Anyone?

>>10087385
How do you know that it's that object the one moving, and not the other you took as reference?
Because you can not know, that is the answer. You can think of the object as if it was motionless.

>>10085464
Both. The fuel evaporation can lead to the effect in the venturi.
The venturi alone would not cause problems in high temperatures (10-30 Cº) as far as I understand.

Which advanced math fields are useful for theoretical chemistry?

>>10087427
Ok, thanks.

One more thing; can the temperature drop be explained by the ideal gas equation (P is proportional to T)?

>>10087463
I believe so.

>don't go to college and start working for three years after graduating high school
>become genuinely interested in physics over the course of this year
>realize I'm pretty much at 11th-grade level and start applying myself
I'm 21, it's not too late to enrol in a bachelor's program, right? Can I hope to make it to grad school?

>>10087545
>worked for 3 years before going to college
you're fine
it'd be significantly worse if you had nothing to show for those 3 years

>>10087563
It was a shit job though, not exactly something that qualifies as valuable work experience.
It feels like I fell behind my peers in a way I can't fix, but I'm probably overthinking it.

>>10087592
it really doesn't matter
having a gap in your work history with nothing to show is a red flag to businesses, but not as much of a red flag to a bachelors program
you're worrying about nothing man

>>10087599
Thanks anon.

Is listening to music while studying really bad? I usually put on light jazz or classical in the background when I do math and it seems like it helps my concentration but I could be mistaken.

>>10087652
I guess the yerkes dodson law would indicate that listening to music while you're tired would be good, but not if you're really alert and caffeinated. Everyone's different though.

>>10087652
I've grown the habit of studying while listening to music to drawn out noise, and I desperately want the silence back.

I was asked to prove that if determinant rows are proportional, then det equals zero.
I said that we could define it as a volume of NxN parallelepiped formed from N vectors, and if at least two are propotional, they are linearly dependent and therefore volume is zero.

OK, this is utter bullshit, right?

>>10087694
yes

Not sure where else to ask this.

Does anyone know what the bumps on either side of the sr 71's nose are?
I notice that some sr 71's have them and some don't. I read they were radar detectors on one site, but another site said they're an aerodynamic feature.
I can't find a good source so I don't know what to think.

>>10087712
How do I prove it, then?

>>10087739
it should be extremely obvious, unless you didn't know that if you multiply any row by a constant it multiplies the entire determinant by that constant
using that knowledge it should be incredibly obvious

Should I take vector calc or diff eq for my classes next semester? I'm not sure which one would come out more useful for me next semester. I only have to take one of the two

>>10087779
well since you've given no info at all about what your other courses are or your major or what semester, i'll just say "diff eq" without any explanation either

How many nukes would it take to make luto warm with volcanic radiation again?

I gave myself a simple mechanics problem to solve - given a launch angle, a distance to a hill, a launch velocity, and the angle of the hill, where on the hill will a projectile land? I found the answer but my question is, is there a simpler way of going about this? I feel like a took a roundabout way of getting to the answer and it could be done more concisely.

>>10081732
How do you get the height to use Bernoulli's equation here? The only method that springs to mind is gravitational potential energy though I wouldn't know how to manipulate it to obtain a result for h. Is there some other method of doing it?

>>10086855
Wow, no specific question as to where you are stuck? Go back to your book and look at heroic definitions and properties of wavefunctions of you can't even determine A.

>>10087800
Stopped reading after you put numbers in. Never do that in the middle of a problem.

Should I retake a class I got a C in for a better grade if I plan to apply to grad school? The class is some Statistics class required for the major (EE) and I did terrible because I skipped almost all the classes and missed a test. If I attend this time around it should be an easy A, but is it worth the time and effort? My gpa is about 3.87/4.00 and replacing the C with an A would push me to 3.90 or somewhere around that.

>>10087234
>>10087236
no one?

>>10087859
>there is no change in height

>>10088036
Pretty sure what you got is what the function is supposed to look like.

>>10088040
Right, so the height should be a constant, I can't find said constant or derive it so what do?

>>10088049
I think so too but why do i get that shape?

Is it possible to guess the lottery through statistics, being I check the most drawn numbers and the intervals in which they're drawn?

>>10088051
>P1+.5pV1^2+pgh1=P2+.5pV2^2+pgh2
>pgh1 cancels pgh2
>solve for V2

>>10088056
I meant that's the shape that's supposed to come out.

>>10088087
it's not tho, it should be like a gaussian bell, smooth

>>10087234
>what i'm doing wrong in matlab
>>10087236
>for k = 1: length(x)

Stop using loops, you retarded code monkey.

x = linspace (-5,5,100);
y = zeros(size(x));
filter = (abs(x) >= 0.5) & (abs(x)<= 1.5);
y(filter) = 1/6 *(5 - 3*abs(x(filter)) - sqrt(-3*(1 - abs(x(filter))).^2 + 1) );
filter = (abs(x) <= 0.5);
y(filter) = 1/3*(1 + sqrt(-3*x(filter).^2+1));
plot(x,y)

>>10087236
>y(k) = 1/6*(5-3*(abs(x(k))-sqrt(-3*(1-abs(x(k))).^2 + 1)));
1/6*(
░░░░5-3*(
░░░░░░░░abs(x(k))-sqrt(-3*(1-abs(x(k))).^2 + 1)
░░░░░░░)
░░░);

You screwed up your parentheses by add an extra set and then closing them mindlessly all at the end

>>10088078
WHAT, IT WAS A COMPARISON QUESTION!? Oh my God, I swear I have brain damage. Holy shit its so obvious now, I might as well start throwing shit across the classroom and riding trolleys through the street, fucking hell.

>>10087694
depends on how you defined determinant really. Just using properties of determinant, you can argue that det being non-zero is preserved under row operations (if you have proved that). Then you have a determinant with a row of 0s. If you're using the sum/product definition of determinant, then having such a row would imply every term in the sum would be 0, then your det will be 0.

>>10087294
The equals key?

>>10087800
if you arent afraid of analytic geometry, then you can try to find the equation of motion of the projectile in terms of x and y, then find your line in terms of x and y (should be something like y=mx+c), then substitute to find your solutions. Using this method you can make your hill be any (reasonable) function

>>10088102
okay so the problem was in the outer bound not in the centre, cool. what's wrong with loops tho? thanks

>>10087545
>>don't go to college and start working for three years after graduating high school

The world would be a much better place if more kids did this.

>I'm pretty much at 11th-grade level

Don't worry. Freshman Physics/Calculus assumes ZERO knowledge from high school. Read Lang's Basic Mathematics to refresh your basics skills before taking a placement exam.

>>10087779
Do both you lazy slob.

>>10088118
Matlab sucks at loops. Vectorize your code.

>>10081912
Wtf even is a tensor? I'm in my final year of a math undergrad and I still have yet to encounter that shit, either in class or on my own. That being said I'm mostly into finite structures and algebra/groups, while I tend to avoid anything involving statistics/engineering/physics, so I'm assuming thats where this shit comes from. I still have To take topology and 400 level linear algebra so maybe it'll come up there (?), but Idk.

>>10088136
scalar -> vector -> matrix -> tensor

>>10088136
read Continuum Mechanics by Gurtin

>>10083996
>...and now clap the one who farted
the trick is there is no trick question dummy, if you feel like you won't pass a mental test than you most likely have an unstable psyche

>>10087545
I was in a top 25 uni for CS (it was a state university and as both an undergrad and a local resident it was a lot easier for me to get in desu senpai), and there was this guy in his mid 30s who never had any prior higher educational experience as a young adult, and went to community college and then some random uni in rural New York where he worked his ass off, got a BA in CS and philosophy in 3 years, and got admitted into the graduate CS program. Idk what his GPA was but I imagine it was good. I actually talked to him about it a little about getting back into school after so long, and he said he had studied philosophy of mind a coding on his own, but hadnt studied much math or anything until he actually got into the Ph.D program, and somehow in his undergrad he only took calc 1 and 2. I certainly dont think it too late.

>>10088066
>being I check the most drawn numbers and the intervals in which they're drawn?
if you check the frequency of drawn numbers over any time period that isn't comically short, you will find that they all occur almost exactly as often.

>>10088005
It depends on circumstances, but usually yes you should.
The extra .03 on your GPA is totally irrelevant, but every graduate committee is going to look over your transcript, and seeing Cs (while it will not kill your application) isn't great.
The one exception to this is if you took the course freshman (or maybe junior) year and have straight As since then. Rough patches early on in university are extremely common and grad schools are fine with this as long as you do well in advanced courses to compensate.

Can someone do my homework.

>>10088261
You have time values, [math]t[/math], corresponding to different temperature values. For example at [math]t = 0[/math] the temp was 180 C.

Plug these corresponding time and temperature values in and see how they dictate what the room's temperature must be.

>>10088218
Yeah it is the only thing close to a C on my transcript and even that semester I got all As otherwise. Took it jr year 2nd semester, and should get As this semester (sr year 1st), but also doing an extra semester then normal (4.5 yrs overall) because of some family things that caused me to do part time for a bit

How do I determine the vectors that form a parallelogram? Linear algebra stuff

>>10088136
Tensors are a multilinear algebra object which are very relevant to algebra. You might see them in 400 level lin alg, but usually they only show up in undergrad for physicists, and they show up in algebra grad studies for math.

>>10088136
>I'm in my final year of a math undergrad and I still have yet to encounter that shit

You didn't see them in linear algebra or abstract algebra?

>>10088005
Did you have any other probability/statistics courses or was it your stochastic processes class? Rather than retaking it, I would take a follow up course and redeem yourself if that was your only probabilistic course. Wasting your time on the same exact course isn't very productive.

>>10088332
Any 2 nonparallel vectors form a parallelogram.

>>10088136
>topology
Now that's the fun stuff, enjoy.

>>10081732
I was asked to prove pic related for my prob and stats exam. We did not discuss multivariate distributions in class, the chapters on multivariate distributions were not assigned, and no homework problems required us to work with multivariate distributions. I was not able to prove the theorem. Should I complain?

what would happen if gravity was negative? like g=-9.8m/s^2

>>10088485
forgot pic

>>10088136
you were given many answers, just keep in mind that physicist and mathematicians have different ideas about what a tensor is. it is simpler to think about it from the physics perspective. but that's not the complete picture

>>10088486

Shit would go flying off the planet, wouldn't it?

>>10082171
what you think now doesn't have anything to do with what you will be thinking after you graduate and start looking for a job. your perspective will change completely and it wouldn't matter much which route you chose and how much fun (or not) you had in college.

I'm studying for a statistics midterm, and I need some help on this problem; I'm a little lost

A full house consists of a three of one kind and two of another kind. Find the probability of a full house consisting of three kings and two queens.

I'm thinking I'll need 4C3 (4 Kings, choose 3), and 4C2 (4 Queens choose 2), but what do I do with the 5 slots they can go in? I assume I gotta do a permuation of 52P5, but I don't know where else to go from there and use the other combinations I got

>>10088486
>implying up isn't the positive direction

>>10088511
Let the sample space equal the set of all possible poker hands disregarding order, then you don't need to worry about the five slots they go in.

>>10088442
Nah we only have that one class for the major.

>>10088430
No. As far as I know a standard intro (200 level) linear algebra class doesnt cover tensorsm. Youll learn manipulating matrices/systems of equations, bases, linear independence, vector space isomorphisms, linear transformations, eigenvectors/values, and perhaps the dual of a vector space, but thats about it. I dont have it with me, but the Ron Larson textbook (which is what I used, although I dont thinks its well known) doesnt even have a section on tensors.

Also in abstract algebra we covered everything in the syllabus and did an intro to to Gallois theory in the last 2 classes, but werent tested on it. Algebra is a really diverse field. Most of the class seemed to be introducing us to the definitions of groups/rings/modules and related stuff and some basic theorems about that shit, but we didnt get too deep. Then on my own Ive studied some stuff about formal languages, "combinatorics on words", and finite groups, but none of it mentioned tensors.

>>10088261
>>10088271
It's Newton's law of cooling, but the numbers of this problem seem wrong. If something cools exponentially, the rate of change decreases -- so it can't cool 8 degrees in the first second and 26 degrees in the second after that.
If the text (kitchen counter, then dishwasher) implies that the thermal conductivity changes for the second second, there's not enough data to solve for all variables.

I have to make a trebuchet for second year mechanical engineering. Has anybody else had to do this and if so can i have a sketch or solidworks file because the mere thought of sitting down and doing this myself makes me want to end it all

>>10083042
Centripetal forces due to our speed
-t. Eng. Application of dynamics

>>10087920
That's the thing, I feel like at that point it would've become an even worse mess in trying to solve for h if I didn't swap all of the variables out for their known values.

>>10088116
Okay, I'll look into this. I don't know much about analytic geometry at this point, but I'll see if I can figure out how to involve it in problems like this.

>>10088485
>Should I complain?
No, you should feel embarassed, you literally just apply the definition of expected value and the first rule for integrals.

>>10087545
I'm 26 and 2 years into my bachelor's of physics and got into my dream University by working hard and fixing my GPA after my 18-20 year old self fucked it up big time. I see things click a little faster for some of the younger students occasionally but that difference seems to be dwindling as I continue to practice and study. It's not too late, don't buy the "your brain is done by the time you're an adult" shit. It's a little tough at first but once you get rolling, you get used to it and your brain gets better at learning. Plus, you're only 21. That ain't shit.

10: 10/10 at 9: 32, Ken? Top speed? Krikan? Do you have bombs in my brain? Koisanman bomb ????
9:32 Krishan = Hasegawa who said the dream and narrow heart? ● Ne-League = Coixman? Image of Dogeza ??
9:19 Does Interfax communication seem to be magical of Kabbal? Fagot? Occurred from Hippolitotal? Hippolitotal

2018/10/23 8: 47 reflection? ● You seem to reflect your idea, do not you? It's better Is this also a Homer relationship? 9: 00 reflection? Hangul?
8: 47 ago, a poor blade? Madman ?? Takahiko? Is it OK? Kanichi ?? ● These groups of Kumamoto Earth Governors and Guru?
Are these Homer relations? Do you have a relationship with my stomach? What about the filth of the left buttocks?
Before 8:47, My nervous relationship with the stomach, Emiko? Who is it? Konchi

>>10088829
What have you tried?

>>10088829
it should be obvious

Given that the union of conjugacy classes is normal, does that mean that any conjugacy class is a normal subgroup itself?

>>10088800
by analytic geometry i mean what you learned in high school

that is, you just need to find the projectile path as a function of x and the hill as a function of x, and find their intersection by making them equal

>>10088486
it's already like that in australia though

>>10088894
Are all conjugacy classes subgroups in the first place? Consider abelian groups.

>>10088804
>apply the definition of expected value
We did not learn the definition of expected value for multivariate distributions,
>and the first rule for integrals
and I'm not sure what you're getting at here. The proof is the discrete case, not continuous.

Writing a pop science article for a college audience. Any recommendations?

>>10085785
Post a link

yo guys, really dumb question. I need to setup a pipe with a slope of 1":30" and need to figure out y at x=48". This is my first time using algebra maths in a real world scenario and am completely lost. I tried finding the lines equation but kept getting busted answer that had a negative answer. Any help would be appreciated and please excuse my pea brain.

>>10089483
> slope of 1":30" and need to figure out y at x=48"

Try thinking about it this way: 1" per 30" means a tenth of an inch every 3 inches. 48" divided by 3" is 16. That's your answer in tenths of inches.

Do math people consider partial functions as valid functions? Is the concept of partial functions relevant in real analysis?

I always thought that a function must have each element of its domain mapped to an element called f(x) in the co-domain. But now partial functions come in and are like "hey fuck you I am not defined for every element in my domain and still am a function, what are you gonna do about that faggot?"

Does this sentence make sense?
Utilise Convolutional Neural Networks to automatically detect [redacted] and learn over time to increase the accuracy of detection using machine learning

It's for a project proposal objective

I'm trying to get dimensions of electric vehicle motors to roughly estimate a design for a class project and am finding fucking nothing relevant. My thought was to just pick a common one and get its dimensions but everything is the fucking vehicle dimensions or random ass irrelevant motors. I'm trying to hunt down the ford focus electric dimensions, as it seems to be the most powerful common one, if that helps you point me in the right direction

Why is cloning illegal?

>>10089891
>tune and apply CNNs to detect [redacted] using machine learning
would probably flow a bit better

if you know which type of learning (supervised,etc.) you want to use already, then replace "machine learning" with that