/sqt/ Stupid question thread

[Anonymous No.7271112]

Let's ask some stupid questions that don't deserve their own thread.
I'll start.

Guys, can I split an equation, derive them, and then put them back together?

For example:

xsinx/(1+2cosx)
= (x/1+2cosx)(sinx/1+2cosx)
derive both then multiply together
etc?

If not, I got that wrong on the test.

[Anonymous No.7271114]

>>7271112
why didn't you just check by splitting x^2 then deriving each term

[Anonymous No.7271124]

>>7271112
Well for starters, this is wrong:
<div class="math">\frac{x \sin x}{1+2 \cos x}
= \left(\frac{x}{1} + 2 \cos x\right)
\left(\frac{\sin x}{1} + 2 \cos x\right)
</div>

[Anonymous No.7271128]

>>7271112

>what is the product rule

[Anonymous No.7271152]

>>7271112
>derivative calculator
what is google ya scrub-muffin

[Anonymous No.7271154]

A comp sci question, not sure if it should go here or /g/ but anyway.

I'm having some trouble with the pumping lemma and breaking it into the three parts xyz.
I get it for the most part, but how do I break up a^n b^2n a^n?
Im assuming x y = a^n and z = b^2n a^n since |xy| <= N however this doesn't seem right to me.
Can someone please clarify this for me?

[Anonymous No.7271160]

>>7271128

I didn't know how to do the product rule and quotient rule together. I completely forgot. Oh well, if this is my lowest test score, the test gets dropped, and my test grade lowest is an 80%, so I'm good.

[Anonymous No.7271171]

how do i proved the peano axioms? i need to do this for a homework assignment due tomorrow.

[Anonymous No.7271190]

>>7271171
Haha, ok since it's homework we can't help you, sorry pal. Now fuck off and google that shit.

[Anonymous No.7271191]

>>7271190
tell me how to proved peano axioms

[Anonymous No.7271212]

>>7271154
Anyone?

[Anonymous No.7271322]

>>7271160
the top function is f(x) and the bottom function is g(x). When using the quotient rule, you do (f'(x)g(x) - f(x)g'(x))/(g(x)^2). Since f(x) is two functions together, you'd only have to use the product rule with regards to f'(x)

[Anonymous No.7271335]

>>7271160

Just set the power to -1 and use the chain rule. I haven't used the quotient rule since calc 1 because fuck it.

[Anonymous No.7271438]

hey guys just a linear algebra question im stumped on,

use the gram schmidt process to find an orthonormal basis for space

W = Span
[4] [-1]
[0] [1]
[3], [0]

sorry this is supposed to be two matrixes

[Anonymous No.7271460]

the verb is differentiate guys not derive

[Anonymous No.7271674]

What is a good way to remember a bunch of math rules in a very short term?

I have a final exam tomorrow and i need to remember all the rules to trig, log and differentiating

[Anonymous No.7271675]

I'm looking for a method for the synthesis of methyl propionate, I know I should be using methanol and propionic acid, while using sulfuric acid as a catalyst, but I need to have a method to show as a source. Anyone knows where I should be looking, all my googling skills failed me so far.

[Anonymous No.7271681]

>>7271675
>Source: Some dude on sci told me so

[Anonymous No.7271687]

>>7271112
sqrt(-1) = i
BUT what does sqrt(i) equal????

Atheists: 0
Btheists: i

[Anonymous No.7271756]

is anyone able to explain in rather simple terms how to perform a BFS and DFS on a graph? the algorithm i have in my course readings are a tad bit convoluted

[Anonymous No.7271761]

Excuse me, i am not english so i higly doubt i'm using the right words here.

In a window with x[0,15] and y [0,15]
F(x)= x+cos(x) intersect on two points with y=x-1

So if i am correct that gives x coordinates for x= Pi and x=3pi.

So that makes: (Pi , Pi-1) and (3Pi -3Pi-1)
Is this correct? and is there another way to write pi-1 and 3pi-1 because this doesnt seem right

[Anonymous No.7271765]

>>7271756
i should mention i have no problems with a and c

it's just b and d that confuse me

[Anonymous No.7271784]

>>7271112
The chainrule is p'U'(p) if i remember correctly,

But what are you supposed to do if you have a formula like:

F(x)= (x^3) + sin(ax+b)

^^^^ I pulled that straight out of my ass so dont blame me if it doesnt make sense.

[Anonymous No.7271785]

>>7271784
What i ment to ask was, i cant just go ahead and say that
f'x= (3x^2) + a cos (ax+b) right?

I had a question in a my book that made me use the chain rule, and then use the other rule (F"G +FG') but i cant remember when this is supposed to be used.

[Anonymous No.7271794]

>>7271756
BFS expands nodes by prioritizing ones with the shortest distance between the starting node and the one your expanding.
looking at (b) it also appears to have a secondary heuristic to expand nodes that have a shorter distance from the root but still have the same distance from the starting node. see dijisktra's algo
A DFS would expand nodes with the greatest distance from the starting node. see greedy search

[Anonymous No.7271799]

Which carbon would act as the most substituted carbon in pent-2-ene? I know that they are both equally substituted, but... if I am trying to do pic related, should I use an oxymercuration-demercuration pathway or a hydroboration pathway?

[Anonymous No.7271810]

HOW do I prove the axiom of choice?

[Anonymous No.7271816]

>>7271785
>>7271784
anyone?

[Anonymous No.7271847]

bumpin

[Anonymous No.7271871]

>>7271799
Acid + H2O, standard formal markovnikov

[Anonymous No.7271873]

>>7271687
i=sqrt(-1)
i^2=-1
i^3=-i
i^4=i
this is the cyclic nature of i, so we know that the 4th root of i=i. But what about the square root? Well let's take i^4=i. take the square root of both sides and we have i^2=sqrt(i). Since i^2=-1, sqrt(i)=-1

[Anonymous No.7271880]

>>7271785
This is correct
You only need chain rule on the sin(ax+b).
For f(g(x), the derivative is g'(x) * f'(g(x))
You did that example right because
g(x) is ax+b so g'(x) is a, then the derivative of sin(u) is cos(u)

[Anonymous No.7271885]

>>7271171
Prove them starting with WHAT?
ZFC?

[Anonymous No.7271886]

>>7271687
>>7271873
Don't spread misinformation
The square root of i is (i+1)/sqrt2

[Anonymous No.7271887]

>>7271335
Agreed, man.

[Anonymous No.7271891]

>>7271885
Just how to proved them. You have to proof your axoims or you could choose something that as false as an axiom.

[Anonymous No.7271893]

>>7271880
Allright thanks! The only question i have left is,
What if it is

F(x)= (x^3) X sin(ax+b)

I completely forgot this one thing formula my professor showed me where you first had to use the chain rule, and then the product rule..

[Anonymous No.7271898]

>>7271871
Cheers m8.
Why is it the case that you use standard Mark?

[Anonymous No.7271906]

>>7271893
You just use the product rule as normal. When you derive the second part you use the chain rule since it's a composite function.

F(x) = g(x)*h(x)
f(x) = g'(x)*h(x) + g(x)*h'(x).

In this case, g'(x) = 3x^2
and h'(x) = a cos(ax+b)
as before.

[Anonymous No.7271910]

>>7271906
nice thanks man!

[Anonymous No.7271913]

What do you guys think of channels like Numberphile and Vsauce?

Sure, they may cause a bit of cringe sometimes but who cares?

Are people mad because they want maths to be a sekrit klub?

[Anonymous No.7271916]

>>7271886
You're right. Our answers have the same magnitude but yours has a complex direction rather than a real one. Very interesting stuff. What course did you learn to derive that?

[Anonymous No.7271917]

>>7271913
Vsauce is garbage. Numberphile is cool.

[Anonymous No.7271919]

>>7271916
http://en.wikipedia.org/wiki/Square_root#Square_roots_of_negative_and_complex_numbers

[Anonymous No.7271923]

>>7271919
>wikipedia
Opinion discarded

[Anonymous No.7271928]

How do i rewrite the following:

2l+2h=120
w+h = 50

It should become volume= w(w+10)(50-w)

This is about a box that can be wrapped with a piece of paper thats 120x50 cm

I get the 50-w but i dont know how to get the w(w+10)

[Anonymous No.7271934]

>>7271886
i^4 = +1 you boob.

[Anonymous No.7271935]

>>7271923
Well the way you derive it is to assume there is a complex solution and then solve algebraically for a,b such that i = (a + bi)^2.
i = a^2 + b^2 + 2abi so we must have
a^2 + b^2 = 0 and
2ab = 1.

[Anonymous No.7271939]

>>7271928
>I get the 50-w but i dont know how to get the w(w+10)
V= L W H m8

[Anonymous No.7271943]

>>7271939
Yes i know that i just dont understand the w+10

>captcha: baked potato = loaf of bread

[Anonymous No.7271955]

>>7271943
yeah idk what shit they're smoking do everything in terms of h

Also I have a feeling you're not describing the problem properly, because otherwise this problem is retarded. You can't evenly cut a rectangular piece of paper to cover an arbitrary box.

[Anonymous No.7271962]

>>7271955
It's a beam shaped box.
H<w<L

[SAGE No.7271965]

>>7271962
You're missing the point. Taking a piece of paper and trying to cover any box with it is not going to work. The cuts you have to try and make overlap. Simple geometric construction does not work. This is a bad question because it cannot be visualized simply.

And you didn't do the math in terms of h. Fuck you.

[Anonymous No.7271971]

How do you cleave alkene rings?

[Anonymous No.7271972]

>>7271965
Why would i do everything in h?

They give me the awnser, i just need to show how to make that formula with the information given.
The piece of paper is exactly 2l+2h long, and w+h.

Thats not that hard to imagine right?

[Anonymous No.7271976]

>>7271972
Nevermind.
I found it

[Anonymous No.7272007]

>>7271976
If you want to know how, its

L x W x H,
H = (50-b)

L= 2l x 2H =120
L= 2l x 2(50-w)=120
L=2l x (100-2w)=120
L= l= 10+w

fill that in LWH,= w(w+10)(50-w)

[Anonymous No.7272034]

>>7271761
It's correct. Furthermore pi-1 and 3pi-1 are real numbers, nothing weird about them, you just can't simplify those expressions due to pi being irrational.

You can find all intersections by solving
x + cos(x) = x - 1
cos(x) = -1
so that x = 2pi*n ± pi for integers n
and thus y = 2pi*n - 1 ± pi.

Your solutions correspond to choosing n = 1 and n = 2 together with the minus sign.

[Anonymous No.7272035]

Quick,
which two numbers are when added 80 and when multiplied by eachother 500
Or do i need to find D for this?

f(x)=(-3x^2)+80x+500=0

[Anonymous No.7272039]

>>7271154
Ah, that's the Pumping Lemma for Regular Grammars. I've only used the PL for Regular Languages.

I'm going to go ahead and give an educated guess on this one:

Assume P is a pushdown automaton with k states that accepts L = {a^n b^n c^n | n >= 0}. Then P accepts strings of the form a^k b^k c^k.
By the PL, we can pump out some portion of this string, and it'll still be in the language L (but it won't have the right form. This will lead to a contradiction.

[Anonymous No.7272049]

>>7272035
You can solve by completing the square.

Start by dividing with -3
x^2 - 80x/3 - 500/3 = 0

The first two terms come from the square
(x - 40/3)^2 = x^2 - 80x/3 + 1600/9

So rewrite the equation as
(x - 40/3)^2 - 1600/9 - 500/3 = 0
(x - 40/3)^2 = 3100/9
x - 40/3 = ± sqrt(3100)/9
x = 40/3 ± 10sqrt(31)/3.

[Anonymous No.7272051]

>>7272049
Last two lines should of course be
> x - 40/3 = ± sqrt(3100/9)
> x = 40/3 ± 10sqrt(31)/3.

[Anonymous No.7272077]

>>7271794
>looking at (b) it also appears to have a secondary heuristic
no they just select the vertices in alphabetical order

[Anonymous No.7272083]

>>7272049
>>7272049
>>7272049
Oh god i am not prepared.
thanks though!

[Anonymous No.7272089]

>>7271891
It doesn't make sense, your axioms define what is true or false.

[Anonymous No.7272141]

>>7272051
This is wrong isnt it?

x is supposed to be 31,892

[Anonymous No.7272153]

>>7272141
>x = 40/3 ± 10sqrt(31)/3.
oh my bad thanks

[Anonymous No.7272311]

do water waves follow the inverse square law?

[Anonymous No.7272330]

>Test, at the 5% level of significance, whether location (Chicago or New York) of the business is related to type of business (privately held, publicly traded or franchise
What kind of hypothesis test is this?

[Anonymous No.7272344]

I have a final exam tomorrow, its 20:00 where i live now.
Should i keep studying until its time to go to bed or should i stop now?

I heard that studying 1 day before exam doesnt work

[Anonymous No.7272349]

>>7272344
Cramming works for the short term (i.e. exam tomorrow), not for the long term.

Ideally, for cramming, you already know the stuff but are just going over it.

[Anonymous No.7272365]

Why the dioxolane ring cannot be formed on the ester instead of the ketone?

[Anonymous No.7272367]

>>7272349
Allright thanks

[Anonymous No.7272439]

Can someone explain me what all the symbols mean?

dU(p)/dx = p 'U '(p)

For example, i need to differentiate:

(X^3)x(X^2) + Cos(ax+b)

How does one do this?
I know that cos(aX+b) is p'U'(p)
So that gives, -asin(ax+b) right?
But now what?


I also remember my professor explained me how to differentiate a formula and he said, here you can just do u'xU
Anyone who can give me an example of this?

Thanks in advance, the only thing i need to know for my final tomorrow..

[Anonymous No.7272442]

>>7272439
>Can someone explain me what all the symbols mean?
>dU(p)/dx = p 'U '(p)

I ment, what is the d, and the /dx

[Anonymous No.7272456]

Is there a relation between quaternions and the " i + j + k " notation for vectors?

[Anonymous No.7272462]

Can anyone show me the proof for Cantor- Schröder-Bernstein Theorem? Is there a specific bijective function that proves it?

[Anonymous No.7272465]

What have I done wrong in this synthesis?
In the first step, I used the Woodward reagent to get the two OHs. In the second, I used the ROMP catalyst. If I have fucked up, what would be a better way to synthesise this product?

[Anonymous No.7272468]

>>7272465
Dammit, I made a mistake with the image.

[Anonymous No.7272659]

How do you factorise square roots?

[Anonymous No.7272675]

https://www.math.rutgers.edu/courses/461/461-s08/001SetTheory.pdf

pg 11

[Anonymous No.7272679]

>>7272675
>>7272462

[somechemist No.7272684]

>>7272468
why not ozonolysis and a grignard?
(the bromocyclopentane is quite cheap anyway)

[Anonymous No.7272687]

>>7272684
Thanks a lot! That works better, but where does the methyl group go?

[somechemist No.7272695]

>>7272468
by the way, ROMP would open a cycloalkene (like the educt), not a cycloalkane like the first intermediate. you might also get in trouble with the the P (polymerisation) part of ROMP because it gives you a long chain.

[Anonymous No.7272697]

>>7272695
So, what are other ways of opening rings that don't polymerise them?
And, as I'm asking you questions anyway,what are non-grignard ways of adding C-C bonds?

[somechemist No.7272698]

>>7272687
knowing how reactions transform your molecules would help you a lot, especially because your first proposed mechanism wouldn't work

[Anonymous No.7272699]

>>7272659
you mean like sqrt(a*b) = sqrt(a)*sqrt(b)?

[Anonymous No.7272702]

>>7272698
Thanks. It just was a little confusing at first, that's all.

[somechemist No.7272706]

>>7272697
forming C-C bonds is one thing, breaking them selectively is another! usually you don't use cyclic starting materials if your product isn't cyclic or a polymer.

a short list of reaction that forms C-C bonds:
Grignard, Diels-Alder, Knoevenagel, Michael addition, Claisen/Dieckmann condensation, Wittig, Benzoin condensation, Li-Organyls, Hyiama, Kumada, Negishi, Stille, Sonogashira, Suzuki, Heck, Buchwald-Hartwig, Wurtz, Ullmann

[Anonymous No.7272708]

>>7272706
Thanks, sempai!

The reason I was using a cyclic starting compound was because the homework demanded it.

[somechemist No.7272709]

>>7272702
you're welcome

and i forgot the highlight of organic reactions in the list above: the Aldol reaction (totally worth learning how it works!)

[Anonymous No.7272710]

IT'S DIFFERENTIATE NOT DERIVE YOU 11TH GRADER
IT'S DIFFERENTIATE NOT DERIVE YOU 11TH GRADER
IT'S DIFFERENTIATE NOT DERIVE YOU 11TH GRADER
IT'S DIFFERENTIATE NOT DERIVE YOU 11TH GRADER
IT'S DIFFERENTIATE NOT DERIVE YOU 11TH GRADER
IT'S DIFFERENTIATE NOT DERIVE YOU 11TH GRADER
IT'S DIFFERENTIATE NOT DERIVE YOU 11TH GRADER

[Anonymous No.7272753]

How much human blood would be needed to amass at least three and a half pounds of high quality iron?

[Anonymous No.7272761]

>>7272442
>>7272439

SOmeone for this?

[Anonymous No.7272776]

>>7272761
please /sci/..
only got a couple more hours until my exam and wikipedia makes it way too complicated

[Anonymous No.7272779]

I know the methods of proving things, such as contraposition, induction, etc.

But how do I best adapt that to a subject I've never seen proofs in? Like I've done basic number theory, but proofs in subjects like Graph Theory stump me because I have no idea how to begin.

I've heard of books like "How To Prove It," but do those actually help or are they just rehashes of the above methods?

[Anonymous No.7272920]

>>7272699
I meant something like such:

(2√3+4)(3√5+6)

[Anonymous No.7272926]

>>7272753
The power of the blood sword can only be weilded by a demon knight who has pledged eternal fealty to Lord Grisnak

[Anonymous No.7273039]

>>7272920
(2√3+4)(3√5+6)
= 6√15 + 12√5 + 12√15 + 24
= 18√15 + 12√5 + 24

[Anonymous No.7273117]

Just guessed my way into a 43/45

and this is the only problem I'm stumped on or am worried to get a single problem incorrect

[Anonymous No.7273238]

>>7272779
read proofs in the subject you want to do proofs in

[Anonymous No.7273245]

>>7271112
since no one bothered the answer is yes you can do it the way you did

[Anonymous No.7273272]

I'm an AE and I was offered a mechanical engineering internship over the summer. My GPA is shit (2.7) so even though it isnt AE should I still do it for hold out for something better?

[Anonymous No.7273292]

What can I do with my math major after college? I feel like I need to pick up a minor or something to flavor this tofu degree.
>What do you wanna do with your life anon?
>Highschool_anon.py: Math.

[Anonymous No.7273295]

>>7273292
write an equation that lets you suck your own dick

[Anonymous No.7273300]

>>7273295
That's y I have so many x's

[Anonymous No.7273304]

>>7273292
try econ or computer science
i am cs and a lot of my ta's and teachers started out as math and later switched to computer

[Anonymous No.7273555]

What do you study in Pure Mathematics? Do I get to learn some fundamental algorithms of shit like differentiation or logarithms?

[Anonymous No.7273566]

>>7273039
Where did the 12√15 come from?

[Anonymous No.7273663]

>>7273566
4*3sqrt(5)

[Anonymous No.7273741]

Why do we write:

<span class="math">\int \int xydxdy[/spoiler]
and not
<span class="math">\int \int xy\partial x \partial y[/spoiler]

after all, we are treating every other variable as a constant

[Anonymous No.7273744]

>>7273741
btw, my
<span class="math">xydxdy[/spoiler]
looks really shitty, how do I add spaces and make it look proper

[Anonymous No.7273747]

>>7273744

[Anonymous No.7273749]

>>7271335
This, quotient rule is literally that anyway.

[Anonymous No.7273756]

>>7273744
\, \mathrm{d} x
erry time
<div class="math"> \int \int xy \, \mathrm{d} x\, \mathrm{d} y </div>

There's also \: \; \quad \qquad for spacing...maybe \.

[Anonymous No.7273759]

is this mechanism plausible for the ring opening for glucose?

[Anonymous No.7273763]

>>7272708
What exactly was the question?

[Anonymous No.7273767]

>>7273763
"Propose synthesis". It gave the starting and ending molecules.

[Anonymous No.7273777]

Does anyone have some images, and information along with those images in which I can look at, and deduce the information that's provided with the image?
Similarly to how Arthur Conan Doyle's Sherlock Holmes applies deduction to humans.
I'd prefer that the provided information be small text in the corner in which the image would need to be magnified to become comprehensible.

[Anonymous No.7273785]

>>7272365
Reaction is under thermodynamic control, and the acetal is more stable than the orthoester (ester is more stable than ketone due to delocalisation). If you dumped a large excess of the diol in you probably would form the orthoester as well, I think, so you have to control the amount of diol you add.

[Anonymous No.7273808]

What's the best method for accurately retrieving the screen coordinates of a single point in 3d world space, if all I have are basic integer/fixed point math functions, and the coordinates of the camera/point as well as pitch/roll/yaw angles for the camera?

I've been trying to read up on rotation matrices and whatnot and have a hard time wrapping my head around them, and don't want to waste time doing the wrong things.

[Anonymous No.7273829]

>>7273808
well people here would be able to provide you with AN answer, but it may not be the most computationally efficient one
you need to ask that to a computer person
but, if you want, try to sketch your situation.

Are you trying to get 3D coordinates from a 2D image or do you have a 3D image which you want to project onto 2D?

[Anonymous No.7273837]

>>7273829
> but it may not be the most computationally efficient one
It's extremely unlikely there'll ever be more than 5 or so of these points at any one time. I'd much rather go for the way that's most easy to implement for a layman such as myself.
>do you have a 3D image which you want to project onto 2D?
Yes.

I want to make certain objects in a first person video game clickable with a mouse cursor, using only the relatively limited functions in the editor's scripting utility. It's "working" right now but the coordinates go way off at high angles because my projection is all whack.

[Anonymous No.7273880]

I've got this in matlab, it's for a 1K texture map so I have a meshgrid from 1 to 1024 with step size 1. I calculated pz, but how do I plot it into a grayscale image like on that picture?
A mesh or surface plot is 3d, I need a 2d image. Also assuming I can get it, how do I export it as tga or png? Sorry I'm a total noob.

[Anonymous No.7273891]

>>7273272
Do it faggot. AE is just glorified ME anyway.

[Anonymous No.7274027]

>>7273566
You're right, it should be 12sqrt(3).

>>7273663
>5 = 15

[Anonymous No.7274037]

>>7273880
imshow(thing,[LowerBrightnessBound UpperBrightnessBound ])
if you want it grey, you need to pick power and upper brightness bounds to be greater (and below) than the actual image's

[Anonymous No.7274065]

>>7273880
you have to learn to google your matlab questions
else, you'll get nowhere

[Anonymous No.7274069]

>>7273837
You can multiply the >>7273837
>I want to make certain objects in a first person video game clickable with a mouse cursor, using only the relatively limited functions in the editor's scripting utility. It's "working" right now but the coordinates go way off at high angles because my projection is all whack.


wouldn't this simply be raycasting from your camera position towards the clicked position on the view plane and then extending the ray until you hit a collider.

It's a special case of raycasting and any game or engine should be capable of dealing with that.

[Anonymous No.7274077]

>>7274037
Thanks that worked perfectly.

[Anonymous No.7274234]

Is anyone familiar with 3D cell culturing?
What method do you use? How different is it from 2D culturing? Any good references/tips?

[Anonymous No.7274362]

Why is pic related true?

[Anonymous No.7274368]

I have a 84% in my Calculus II class and a 88% in Linear Algebra. Final Exam is worth 200 points in each class. I already have the necessary points to get a 70% in Linear Algebra, and I need 83 points to get a 70% in Calculus II. What are my chances of passing Calculus II?

[Anonymous No.7274371]

>>7274362

[Anonymous No.7274377]

>>7274362

<div class="math">
\sqrt{x^{5}y} = \sqrt{x^{4}xy} = x^{2}\sqrt{xy}
</div>

Just factor out the x^4.

[Anonymous No.7274382]

>>7274234
>How different is it from 2D culturing?
I'm not enormously familiar but it's much more challenging because most epithelial cells are perfectly happy to form a single cell layer in culture for a while but getting them to grow on one another either requires cancerous cells (like HeLa) or cunning use of growth factors. Obviously, if you're growing something to implant then the former is a bad idea.

[Anonymous No.7274384]

>>7274362
Yeah, multiply x^2 times x^3 which equals x^5 then factor out x^4

[Anonymous No.7274385]

>>7274371
Gee, I'm an idiot, thanks.

[Anonymous No.7274444]

>>7274368
below 70 fails? they must make the exam very easy lel

[Anonymous No.7274468]

>>7274444
Overall class grade is based on points. If I get a 0 on the final for Linear Algebra I still come away with a C. Calculus II is where I still haven't passed.

[Anonymous No.7274470]

How are graduate classes graded?

It says "Based on class participation" but what does that really mean?

[Anonymous No.7274510]

>>7274470
that makes no sense
if it means what i think it means, it basically means the prof will give you whatever grade he feels like
but it can't be so
what is the subject?

[Anonymous No.7274530]

>>7271112
This one always get some weird answers, I'm almost asking this as much to start a debate as I am to get a definite answer.

"X is a continuous random variable, what conditions must be satisfied for X to be well modelled by a Normal Distribution?"

[Anonymous No.7274543]

>>7274510
"Our main objective will be to understand how the differential topology of a 4-manifold constrains the curvature of the Riemannian metrics it supports. Topics will include Seiberg-Witten theory, self-dual metrics, Kähler-Einstein metrics, and conformally Kähler geometry."

[Anonymous No.7274556]

>>7274470
Graduate classes are graded however the prof wants to grade them. I've had one mandatory class with three exams plus graded homework for 25% of the grade, and another mandatory class with 100% graded homework and no tests (until quals came anyway.)

[Anonymous No.7274586]

>>7274530
What a bullshit question
Depends on how accurate we want to be

[Anonymous No.7274591]

>>7274556
it is so unfair, people with friends would be able to compare answers

[Anonymous No.7274751]

How do you simplify the first thing through factorisation to get the result pointed here?

[Anonymous No.7274753]

>>7274751
You factor out a root(8) and then realize that what's left under the radical is (x+5)^2. srsly.

[Anonymous No.7274756]

>>7274751
8x^2+80x+200=8(x^2+10+25)=8(x+5)^2
and you can figure the rest out.
btw it should be |x+5|

[Anonymous No.7274759]

>>7274753
>>7274756
Sorry guys, I'm not normally this stupid for algebra. Thanks.

[Anonymous No.7274825]

>>7273238
this one was easy

[Anonymous No.7274874]

How many grad classes is too much for an undergrad

Are they exponentially more difficult than a difficult upper division undergraduate class?

[Anonymous No.7274883]

https://youtu.be/wUyHeXkKL9A?t=173
I understand that "perpetual" machines usually require some initial energy, and will eventually stop, even if it takes ages.
But what about magnets? This machine for example. Where does the energy come from? And also, will it ever stop?

[Anonymous No.7274904]

>>7271675
Look for patents and existing facilities, or use Ullmanns enciclopedia.

[Anonymous No.7274971]

>>7274751
>>7274753
are we literally doing highschool homework now?

[Anonymous No.7274977]

does your brain use any more calories when under metal exertion such as studying, test taking, or problem solving?

[Anonymous No.7275023]

Why is (e^[x^2 + 4]) / (e^[x^2 - 4]) = e^8?

[Anonymous No.7275060]

>>7275023
because e^(x^2+4)=(e^x^2)(e^4)
so the (e^x^2) cancels and you have (e^4)/(e^-4) which is equal to....

[Anonymous No.7275072]

>>7275060
Damn, I've been 20 minutes here trying to derivate the division I don't know why. I should get some rest. I'm rusty as fuck.

>>7274971
Sorry m8, it's been so long since high school. I'm trying to remember some stuff here and there.

[Anonymous No.7275073]

>>7274382
I don't think my advisor wants layers of cells. I think what they're looking for is a suspended cell to freely grow so that the morphology would be more similar to the body's.

No implants. I'm working with cancer cells (pancreatic and colorectal) and treating them with a few different drugs.

[Anonymous No.7275098]

>>7271674
study pleb

[Anonymous No.7275108]

>>7271112
Is every convergent sequence bounded or just ones with the absolute difference metric?

[Anonymous No.7275185]

>>7271674

Associate what you've read with what you've read before it, making a long chain of mental associations.

Frequently actively recall information you've read.

Create and take multiple short quizzes on the information you'd like to memorize.
Also, don't make the quizzes open book.

PS: Get a very good night of sleep!

[Anonymous No.7275193]

>>7271674
>remember
lel
We're humans!
We use tools like IPhones and written language to our advantage!
>take water bottle
>remove label with precision
>scan label
>put answers sheet on the ingredients list and what not
>print out
>secure on water bottle
>profit

[Anonymous No.7275210]

Is mayonnaise an instrument?

[Anonymous No.7275353]

>>7275210
That sick shit is an instrument of torture!

[Anonymous No.7275410]

can someone give me a layman's interpretation of time dilation?

I know basic astronomy, if that helps.

[Anonymous No.7275416]

>be me
>take Calculus II at a community college
>5 test and one gets dropped
>end up with a B
>final exam
>professor gave us the option to skip the final and end up with whatever we got from the four test


Is this how it is at a community college, /sci/? How bad am I gonna suffer later on if I ever go to a university? I mean, I thought the professor was good and not easy or hard, just right. Out of 30 students, 4 dropped, and 13 got Cs. In other words, this professor wasn't an easy A professor. Am I gonna survive at a university in USA? I'm a CE or EE major.

[Anonymous No.7275425]

What should a (pure) math major who wants to go to graduate school be doing at the halfway point of their undergraduate career?

So far, I have done:
- an uncredited seminar in mathematical physics
- won an amateur level programming competition
- have a 4.0
- taken classes through proofs, ODEs, and Linear Algebra, doing Abstract and Analysis next semester

I know I'm behind, but I'm doing a small research project next semester (and probably for the next 2 or 3, although the topics very from semester to semester). I also do a lot of light independent reading, so I'm familiar with a lot of different types of math, but only on the surface.

[Anonymous No.7275458]

>>7275410
Classical electrodynamics and newtonian physics don't mix well. Electrodynamics says the speed of light is always the same, but according to Newtonian physics observers would make different observations of the speed of the same light if they are moving at different speeds with respect to each other! Special relativity is how one starts out trying to fix this issue. The theory can be presented as the consequences of simple logic experiments with certain assumptions. In addition to a phenomenon called "length contraction" (due to which moving objects appear compressed with respect to one of their dimensions) there is also "time dilation". If a thing does not have the same velocity as you then it seems slowed down with respect to your observations by a factor dependent on speed. One continues trying to fix these issues with general relativity, in which there is also time dilation due to forces on the observed object (and in particular gravity causes time dilation to everything it applies to.)

[Anonymous No.7275465]

>>7275410
>everything in universe is made of balls
>'time' moves forward when shit happens
>'time' moves forward when balls interact, etc.
>two people moving back and forth really fast throwing ball
>two people standing still throwing ball

>moving causes greater distance for ball to travel cuz longer distance motherfucker hypotenuses

>so 'time' goes slower, since balls touch slower

[Anonymous No.7275470]

WHEN
H
E
N

[Anonymous No.7275482]

>>7275416
Not all CC are like that. I've had calc teachers that made the content so hard/convoluted that the class average was around a 50. If you didn't drop the course and was around the class average he curved you up to a C or a low B after the final. Raped my GPA, but made me dedicate 10 times the amount I would have regularly set aside for it.

That being said I know some unis that let students use ti89 or better calculators the entire time. So the students just had to work backwards (calculator would get the answer) so they could 'show the work'.

[Anonymous No.7275562]

Can someone explain how to get a quadratic equation from a table?

[Anonymous No.7275574]

>>7275562
Locate the table, pick up the quadratic equation.

[Anonymous No.7275575]

>>7275562
>>7275574
Protip: Use both hands.

[Anonymous No.7275831]

>>7275562
Extract it. It usually takes a crane to get them out.

[Anonymous No.7275838]

>>7275108
boundedness depends on the metric, convergence only on the topology. Every set is bounded in a bounded metric, and a bounded metric can sometimes induce the same topology as an unbounded metric over a space.

[Anonymous No.7275847]

>>7274883
>>7274883
Is this too stupid even for the too stupid thread?
Sorry about that.

[Anonymous No.7275875]

>>7275838
I'm studying real analysis right now so I only have a taste of topology.
> bounded metric
bounded metric space?
because that's what google turns up
> Every set is bounded in a bounded metric
https://proofwiki.org/wiki/Convergent_Sequence_in_Metric_Space_is_Bounded
I was reading this and couldn't figure out why.
for all i : d(x_i,l) < M implied for all i: b< x_i< B
This statement shows that?

[Anonymous No.7276016]

>>7275875
By bounded metric, I assume he means the metric given by <span class="math"> \overline d (x,y) = \min \{ d(x,y), 1\} [/spoiler]

[Anonymous No.7276160]

"Two narrow, parallel slits in an opaque barrier are separated by 0.4 mm. When the slits are illuminated by a distant source of electromagnetic waves, at normal incidence, which wavelengths have interference maxima at an angle of 40 degrees to the straight-through d?"

My question is whether there is a limit to how many wavelengths would produce a maxima. Wouldn't it just keep going as along as mL=2dsin(theta)?

[Anonymous No.7276228]

>>7276160
Yep.