Stupid Questions Thread

[Anonymous No.7956813]

Stupid questions thread ITT

I'm reading the lecture notes for a class I didnt attend and it says that the commutator relation [math][\hat{J}_z, \hat{J}_\pm]=\pm\hbar \hat{J}_\pm[/math]

Where [math]\hat{J_\pm}=\hat{J_x}\pm i\hat{J_y}[/math] and [math][\hat{J_i},\hat{J_k}]=i\hbar\epsilon_{ijk} \hat{J_k}[/math],

but I think this is wrong and it should be instead [math][\hat{J}_z, \hat{J}_\pm]=\mp\hbar \hat{J}_\mp[/math]

Is it true?

[Anonymous No.7957038]

bump

[Anonymous No.7957076]

>>7957038
accepted. after someone explains to me wtf shes doing there!

[Anonymous No.7957100]

>>7957076
she's trying to make some super mardi gras beads

[Anonymous No.7957103]

>>7957100
no shes manually repairing wale DNA
or bronchosaurus..

[Anonymous No.7957365]

>>7956813
Why don't you write it out you stupid ass?

[Anonymous No.7958015]

>>7947410
But it literally is? [eqn]A=πr^2[/eqn], so [eqn]π(2r)^2=4πr^2=4A[/eqn]

[Anonymous No.7958021]

>>7956813
Your commutator relationship is wrong. Should be [math][\hat J_i, \hat J_j ] = i \hbar \varepsilon_{ijk}\hat J_k[/math]

Type up your work in deriving the wrong answer and I can point out your mistake(s).

[Anonymous No.7958022]

>>7956813
If you already know it all then why are you in the class?

[Anonymous No.7958071]

>>7956813
why is she injecting watermelonium into the nucleotide

[Anonymous No.7958129]

Is there a reason behind having a crooked/asymmetrical nose? I haven't fallen and hurt my face ever.

[Anonymous No.7958131]

Is this considered a proof?

[Anonymous No.7958132]

Can someone explain just what the h*ck Griffiths did to get script r?

[Anonymous No.7958140]

The correct relation is [math] \displaystyle [\hat{J_i},\hat{J_j}]= \sum_k i\hbar \epsilon_{ijk} \hat{J_k} [/math]. With it you get

[eqn][\hat{J}_z, \hat{J}_\pm] [/eqn]
[eqn] = [\hat{J}_z, \hat{J}_x] \pm i [\hat{J}_z, \hat{J}_y] [/eqn]
[eqn] = i\hbar \hat{J}_y \pm \hbar \hat{J}_x [/eqn]
[eqn] = \pm \hbar \hat{J}_\pm[/eqn]

[Anonymous No.7958145]

Could you guys please stop opening up Stupid Question Threads when there are already several open?
Post in the old one, or (if you want to guarantee the attention) post your question as a standalone question.
But don't make us need to keep up with several long threads at the same time.
Thank you!

[Anonymous No.7958148]

>>7958132
He used the law of cosines on the triangle in the pic?

[Anonymous No.7958152]

hypothetically speaking, what kind of STEM related job could i get with a Physics bachelors assuming i didn't go for a Msc?

[Anonymous No.7958153]

>>7958148
Oh thanks man

[Anonymous No.7958154]

>>7958152
Coffee barista

[Anonymous No.7958155]

>>7958152
>assuming i didn't go for a Msc?
IT is the biggest sector, if you want to stay in science and engineering statistically you'll be a lab tech mostly, but it largely depends on your background, experience and network.

[Anonymous No.7958157]

>>7958155
i have 3D programming experience with C++. does that help?

[Anonymous No.7958190]

>>7958157
so youre an employer looking for a programmer, is he going to choose the physicist who only has a bsc or a programmer/software engineer?

there is an ongoing trend here in this shitboard that people who study physics can do anything they want if they really really want it, dont listen to them

[Anonymous No.7958195]

>>7958190
but then what if i show experience in the area he's interested in? say fluid sim or rigid/soft body dynamics.

i'm not saying i could do those areas because i have a bsc, i'm just trying to weight my options. i'm not even doing the degree yet. it's just that i'm worried about the tradeoffs of what i will study versus my job prospects, primarily due to the disparity i see in industrial R&D and academia, so i wanted to know where physicists stand in that regard beforehand.

[Anonymous No.7958211]

>>7958190
also the program i'd be taking is a physics-mathematics honors specialization, so i'd be able to do a Msc in the future, but i wanted to see if there were employers that would cover it. i heard from a friend of mine that many CSfags and engineers get their degrees covered, but since they're so ubiquitous in the industry it wouldn't be possible with a physics major. is that also the case?

[Anonymous No.7958309]

I love computers. I'm very town about what I should take in college. Top 30 for all engineering courses, not sure what the math ranking is but I'd imagine it's not far behind.

I use to love programming but fell out of love when my teacher forced me to learn from scratch even though I was programming 4 years prior to high school. I felt like that's what the market would be like, a boss telling me exactly what to do and how to do it.

Now I'm torn between being an SE or CE. Never worked with circuitry before but I'm not sure how I'd like it. Could be fun as shit. Always wanted to know exactly how everything worked.

I really want to do cryptography too. I'd like to work until I clear my debt and then try to start my own software firm dealing with security, storage, backups, etc... I have an in with a local security company that has corporate and government aspirations. I know they handle physical security but could that lead to an in for corporate data security in a world where online presence is everything?

Tl;Dr Should I major in Math and minor in CS or should I do CE with like a physics or Math minor?

[Anonymous No.7958310]

>>7956813
I'm being retarded.

Let's say I want to integrate, from -pi to pi, e^(a*ix) with respect to x.

Why is this wrong?
[eqn] \left[ \frac{1}{ai} e^{aix} \right]^{\pi} _{- \pi} = \left[ \frac{1}{ai} (e^{ix})^a \right]^{\pi} _{- \pi} = \frac{1}{ai}(-1)^a - \frac{1}{ai}(-1)^a=0[/eqn]

[Anonymous No.7958339]

>>7958132
Look literally right above your post

[Anonymous No.7958371]

>>7958339

Is what I posted considered a proof?

And damn, what a fucking coincidence that I posted the answer to his problem 1 post before he asked his question.

[Anonymous No.7958383]

>>7958371
No it's not a proof, it's a bunch of operations and observations that will aid you in the process of writing a proof. You have to use more words and treat mathematical statements just like regular english statements; use punctuation. You might also find the implication arrow handy.

[Anonymous No.7958385]

b^x · c^x = (b·c)^x
is valid when b, c are are in (0,\inf) and x is in R.

exp(i·pi)^x · exp(i·pi)^x = (-1)^x · (-1)^x isn't 1^x.

lrn2complex number arithmetic.

The rules from cardinal arithmetic, where
m^n = |{1,2,...,n} -> {1,2,...,m}|
doesn't straight forwardly generalize to R^2 and the field operation that gives you C.

[Anonymous No.7958390]

>>7958310
b^x · c^x = (b·c)^x
is valid when b, c are are in (0,\inf) and x is in R.

exp(i·pi)^x · exp(i·pi)^x = (-1)^x · (-1)^x isn't 1^x.

lrn2complex number arithmetic.

The rules from cardinal arithmetic, where
m^n = |{1,2,...,n} -> {1,2,...,m}|
doesn't straight forwardly generalize to R^2 and the field operation that gives you C.

[Anonymous No.7958392]

>>7958383
Also look here: http://www.math.caltech.edu/~2014-15/3term/ma011/..

Under resources download the first file and read through the beginning section.

[The Fairy Queen No.7958394]

>>7958140
Yeah, thanks, I forgot the minus sign from the second epsilon

[Anonymous No.7958396]

>>7958390
Thanks man... I sware I knew that shit, but I can't find it in my head any more.

[Anonymous No.7958610]

[latex]\frac{1}{2}[\latex]

[Anonymous No.7958646]

Write, so for euler's equations for angular velocity, without forcing the solutions can be thought of as the intersection between the two ellipsoids given by the equations of the conserved properties

[math]
E = \tfrac{1}{2} A \omega^2_1 + \tfrac{1}{2} B \omega^2_3 + \tfrac{1}{2} C \omega^2_3 \\
[/math]
[math]
H^2 = A^2 \omega^2_1 + B^2 \omega^2_2 + C^2 \omega^2_3
[/math]

But when there's forcing, as shown below, this obviously ceases to be true. I suspect that the solutions now lie on the surface of a cone, but I've fittered around, and have no idea how to prove this.

[math]
A \frac{d\omega_1}{dt} + (C-B) \omega_2 \omega_3 = -k \omega_1
[/math]
[math]
B \frac{d\omega_1}{dt} + (A-C) \omega_2 \omega_3 = -k \omega_2
[/math]
[math]
C \frac{d\omega_1}{dt} + (B-A) \omega_2 \omega_3 = -k \omega_3
[/math]

[Anonymous No.7958648]

So I have a project where we have to construct a truss out of either sitka spruce or basswood capable of holding 1000 lbs. (Although more is obviously better, 1000 is just the ideal) I'm working with a range of around 22 x 7 inches.

I've been looking at bridges for a while, and it seems like the best options are the pratt truss and a K-Truss design. Howe and Warren don't seem to be any more efficient.

Given the constraints, should I model it after one of these types of bridges? It seems that the K-Truss, although might be extremely difficult to build, would hold a lot of weight. However, at a scale like this, can it be as efficient as a pratt design? There is a factor of materials, weight, and thus efficiency I want to account for as well.

[Anonymous No.7958662]

>>7958648
How are trusses hard to build?

[Anonymous No.7958683]

Just looking for some feedback on a proof.

>If [math] K [/math] is a compact set, then [math] Sup ~ K [/math] exists and is an element of [math] K [/math]

Let [math] K [/math] be a compact set, then [math] K [/math] is bounded, so that for all [math] x \in K [/math] there exist an [math] M \in \mathbb { R }[/math] such that [math] |x| \leq M [/math], which is to say [math] M = Sup ~ K [/math], so [math] Sup ~ K [/math] exists. Next we show that [math] M \in K [/math]. Let [math] \left ( x_n \right ) [/math] be a sequence in [math] K [/math] which has [math] M [/math] as a limit, since [math] K [/math] is compact it is closed so [math] M \in K [/math] [math] \blacksquare [/math].

[Anonymous No.7958686]

>>7958662
Well it isn't that it is necessarily HARD to build, but I'm working with members with a width minimum of 1/2 an inch, so my concern is that given the limits put in place, it might be too cramped to allow the members to be in compression and tension properly.

I'm away from home, so it's a little tougher for me to draw things to proper scale currently, so I was just brainstorming and wondering if anybody had any insights.

[Anonymous No.7958697]

>>7958683
The first bit is funny. M=Sup K isn't really the right thing to say. The supremum is defined as the lowest upper bound, so the thing to say is that because M is an upper bound there exists a lowest upper bound and hence a supremum. Also, a description on how to get that sequence would be nice.

[Anonymous No.7958699]

Math is like weaving thread out of fiber while programming is like making quilts out of fabric
y/n ?

[Anonymous No.7958715]

I'm not a scientist but I whenever I cook pasta I notice that when I boil water and turn down the heat there appears to be more steam coming after I remove the heat source. Why is this?

[Anonymous No.7958716]

>>7958715
The steam is condensing nearer the pot when you turn down the heat.

[Anonymous No.7958723]

>>7958716
So essentially
>boiling
>remove heat
>temp drops
>some of the water is hotter and then turns to steam because the avg temp of the water is cooler
or something like that?

[Anonymous No.7958724]

>>7958699
I've seen worse analogies. Thinking about the accumulated effort represented by the hardware and software I use makes me shudder.

[Anonymous No.7958734]

>>7958723
What he means is a sequence like this:
>You turn off the heat.
>The air around the pot becomes cool faster than the water because air moves around.
>The moisture capacity of the cool air is less than the moisture capacity of hot air so the water vapor coming off the hot water starts condensing above the pot.

[Anonymous No.7958742]

>>7958734
Oh shit that's pretty neat.

Thanks anon!

[Anonymous No.7958832]

Almost a freshmen in college here.

I look at your advanced maths and I get dumbfounded. I have no idea what I'm looking at. It looks dark and scary. Is this because I have no idea what I'm looking at? It won't be so bad once I actually learn it? I want to major in Math, currently don't have enough time to study myself before college. Will it get better as I learn? It's like looking at programming to a non programmer right?

[Anonymous No.7958859]

>>7958832

Hah. You're just normal.

I remember my freshman year when I got into research, and my professor sent me some papers to "skim through". It looked like fucking hieroglyphs.

It's 3 years later now, and I've learned so much that most of that shit is casual before-bed reading.

You'll be fine.

[Anonymous No.7958866]

>>7958859
Fuck yeah. Thanks buddy I appreciate it.

[Anonymous No.7958871]

How do you go from left to right?

[Anonymous No.7958891]

>>7958871
I have a feeling that equality is wrong.
If you multiply what's inside the logarithm of the left side by the conjugate, you get [math]\frac{x^2}{x(2+\sqrt{x^2+4}}[/math]

[Anonymous No.7958899]

>>7958891
That's what I though. The intention was to put the x on top to avoid dividing by zero. Here's the end result.

[Anonymous No.7958933]

>>7958390
>b^x · c^x = (b·c)^x
>is valid when b, c are are in (0,\inf) and x is in R.
Not the anon you're replying to, but are you sure that's right? I'm pretty sure that rule is valid for any real b and c. Got a counterexample?

[Anonymous No.7958943]

>>7958683
Incorrect. First of all the [math]M[/math] you have there isn't [math]\operatorname{sup}K[/math]. The existence of [math]\operatorname{sup}K[/math] is already guaranteed by the definition of bounded, so you don't even need [math]M[/math]. Second, you have to show that the supremum is a limit point from definition of a supremum.

[Anonymous No.7958944]

So I'm learning about sensors and reading about potentiometer based displacement sensors. The circuit on the right linearizes the output voltage when you load the voltage divider, apparently. But I'd like to know how to derive the formula on the bottom of the page. When I use nodal analysis on the node that the wiper forms, I get a much messier answer. i 'd just like to understand. Thans in advance

[Anonymous No.7958948]

>>7958933
[math]-2 \sqrt{-2}\cdot \sqrt{-2} \ne \sqrt{(-2)\cdot (-2))} = \sqrt{4} = 2[/math]

[Anonymous No.7958950]

>>7958933
Pretty sure it's true if you stay strictly in the reals. However as soon as you introduce anything producing a non-real number, you're fucked. Someone will correct me if I'm wrong.

[Anonymous No.7958952]

>>7958933
[math] \sqrt{-2}\cdot \sqrt{-2} = \sqrt{-2}^2 = -2 [/math]

[math] \sqrt{(-2)\cdot (-2))} = \sqrt{4} = 2 [/math]

[Anonymous No.7958953]

>>7958944
Forgot picture

[Anonymous No.7958954]

>>7958933
b is any negative number, c is any positive number, and c is 1/2

[Anonymous No.7958955]

>>7958952
Shit anon, you've just blew my mind. I've probably been making that mistake for years. Was >>7958950 right?

[Anonymous No.7958958]

>>7958954
Shit, I meant x is 1/2, but I'm sure that was clear.

[Anonymous No.7958960]

>>7958954
>>7958958
God dammit, and b and c are BOTH negative.

[Anonymous No.7958998]

>>7958390
>>7958933
>>7958955
Fuck it, since this thread is teaching me shit I didn't know, I'll ask something else. How was b^x · c^x = (b·c)^x relevant to the original anon's thing anyway? i.e. how does it related to e^(aix)=(e^ix)^a ?

[Anonymous No.7959013]

>>7958955
Both answers are correct in the complex plane, because square roots are multivalued in the complex plane.

[math]\sqrt{-2}=\pm\sqrt{2}i[/math]

[Anonymous No.7959051]

>>7958955
This guy >>7958950 is right, >>7958952 is an idiot or a troll.

[math]\mathbb{R}-sqrt:[0,\infty)\to\mathbb{R}[/math]

[math]\mathbb{C}-sqrt:\mathbb{C}\to\mathbb{C}[/math]

taking roots in the complex plane is a multivalued function.

[Anonymous No.7959074]

Should I take an extra 8 classes my senior year and get a double major in pure and applied math?

I only need real analysis to complete my pure degree next year, also want to take a graduate level course in the fall.

[Anonymous No.7959144]

Is it a scam?

[Anonymous No.7959171]

>>7958715
Steam is invisible. Cooler, condensing steam is what you see. So, reduce the heat, steam cools into condensing vapour earlier.

[Anonymous No.7959265]

>>7959051
The solution to [math]x^2=3[/math] is [math]\{ +\sqrt{3} , -\sqrt{3} \}[/math].
The different branches of complex functions, Riemann geometry etc. don't make the square root multi valued as a function.
But at some point I guess we're fighting over semantics.

[Anonymous No.7959434]

>>7958646
Anyone got any ideas? >_<

[Anonymous No.7959437]

>>7959074
Extra 8 classes sounds like a pain the ass for 1 year

[Anonymous No.7959456]

>>7959437
I should mention that it's the quarter system, so that's more like 16/3 classes or about 5 classes equivalent in the semester system.

[Anonymous No.7959607]

It's valid to go from [math](A\vec u) \cdot \vec v = (A^t\vec u) \cdot \vec v[/math] to [math]A=A^t[/math] (where [math]A^t[/math] is the transpose of matrix [math]A[/math] and [math]\cdot[/math] denotes the dot product, of course), right? It makes sense that it would be true but I'm not quite sure how to simplify the first equation into the second since the dot product doesn't have some inverse operation as far as I'm aware.

[Anonymous No.7959633]

>>7959607
If it holds for all u,v, then yes. If specific u,v then no.

[Anonymous No.7959680]

>>7959607
Let [math] (\cdotp ,\cdotp): V\times V \rightarrow \mathbb{R}[/math] be a scalar product on [math]V[/math], then [math](u,AV) = (u,A^{T}v)[/math] implies [math](u,(A-A^{T})v) = 0 \quad \forall u, v \in V[/math], so by definition of the scalar product we have either [math]u = 0[/math] or [math](A-A^{T})v = 0[/math]. The first is incorrect, so [math](A-A^{T})v = 0 \quad \forall v \in V[/math] leads to [math]A-A^{T} 0[/math], or [math]A=A^{T} [/math]

[Anonymous No.7959702]

>>7958648
Anon, I did a project related to this and had the highest weight held/weight of bridge ratio in my class. Modeled mine after a truss and added some components of a Pennsylvanian petit truss. Make sure your joints are well put together; they're arguably the most important part of making your bridge remain unbroken. Just my two cents, good luck anon

[Anonymous No.7959872]

>>7959702
Cheers anon. I'll start crunching some calcs on it tomorrow to see if it puts any strain on the members, looks interesting and should be possible given my member constraints. I'll take a look at it, and I appreciate the suggestion!

[Anonymous No.7960018]

Is it bullshit?

[Anonymous No.7960051]

>>7960018
yeah

[Anonymous No.7960067]

How does osmosis work?
Diffusion down solute concentration gradient doesn't explain it completely accurately.

[Anonymous No.7960090]

is he right
https://www.youtube.com/watch?v=_j9wms5KpWQ

[Anonymous No.7960096]

I got one

If humanity (or living creatures in general) exist for another billion years and there are no biological changes observed in any living thing, would that disprove evolution?

[Anonymous No.7960236]

>>7958309
major in maths everyone and their mum has a CS degree nowadays you missed the boat for that by a couple decades

[Anonymous No.7960251]

>>7960236
Cool thought so. I guess maths + CS minor give me a wide array of options. Should I take anything extra in order to get into things like finance? What's needed for that? It doesn't interest me too much apart from my plans to own stock and flip real estate later in life. But if I'm gonna have the degree for it I might as well have a backup plan if CS doesn't work out.

[Anonymous No.7960253]

What's the point of this identity? Seems trivial and useless.

[Anonymous No.7960277]

>>7960253
Never underestimate the power of symmetry, or in this case anti-symmetry.

[Anonymous No.7960291]

>>7960251

make the post on /g/ and you get CE + physics/math

this is a math board what did you think people would say.

[Anonymous No.7960304]

>>7958832
>>7958859
yeah basically it looks tragic because you don't know the symbols, when you do know the symbols it's pissbaby shit

i've never actually seen anything hard that isn't impossible on /sci/

[Anonymous No.7960306]

>>7960067
does it not?

[Anonymous No.7960389]

>>7960291
/g/ is my home but it's the most toxic backwards ass community on this website. it's worse than /b/ or at least it's equivalent.

I think I want to go maths because of the range of options. I can get into finance, teaching, computer science. I can go to grad school. I'm sure there are decent programs for me to get into as a math major. I can be happy with a lot of work as long as I get a decent paycheck and I'm not stressing over my bills every week.

[Anonymous No.7960400]

>>7960277
Friend, antisymmetry is NOT that. It's a property of relations that satisfy
If a~b and b~a then a=b

[Anonymous No.7960413]

>>7960090
Tesla wasn't aware of E=Mc^2, so he can't be commenting on that.

Anyway, E certainly does not equal MC^2, that would be ridiculous.

[Anonymous No.7960423]

I'm studying General Biology using Campbell Biology book, while the book is pretty good I feel that the lack of practice problems are big problem since I can't really make sure I'm learning what I'm reading, Does someone know a good book/site for practice problems that I can use together with the book?

[Anonymous No.7960434]

>>7960400
>words can't have multiple meanings
>in math of all fields

[Anonymous No.7960564]

How do I compute the commutation relation of the P^2 and X operators? So [math][p^2,x][/math]. I know the answer is [math]-2i\hbar[/math], but I don't know how to get there.

Sorry I can't really into latex, so just image the hats are there.

[Anonymous No.7960595]

>>7960564
The answer should be [math]-2i\hbar p [/math] not [math]-2i\hbar[/math], my bad.

[Anonymous No.7960620]

>>7960564
[p*p,x]=p[p,x]+[p,x]p=-2ihp
product rule exists for commutators too

[Anonymous No.7960629]

>>7960620
Thanks mate, I thought it was probably easy, but sometimes I just don't see it.

[Anonymous No.7960632]

>>7960629
>sometimes I just don't see it.
Happens to all of us

[Anonymous No.7960633]

>>7960067
It's a good one for younger pupils to visualse with dice, a bit like half lives.
You need a lot of dice, I've done it with 200 white dice and 30 red dice.
Split the white dice into two piles of 100. Remove 15 from pile A and add it to pile B, then add your red dice to pile A.
Now set your rules. For a fully permeable membrane / naked diffusion you can move dice of either colour when they roll a 6 (e.g. move from pile A to pile B and vice versa).
After a while you end up with a relatively homogenous mix.
You can do selective permeability by saying that no matter what the red dice roll, they can't move sides. After a while you get a disproportionate amount in Pile A.
You can even do reverse osmosis by making the rolls proportional to the number of dice on one side.

[Anonymous No.7960637]

>>7960096
I'm pretty sure I'm not a carbon copy of my parents, but yeah, sure.

[Anonymous No.7960737]

Can someone explain this. How the fuck can 30 degrees have a negative sine when 30 degrees is in the first quadrant (where sine and cosine are positive).

[Anonymous No.7960756]

>>7960737
Are you illiterate? That's not what the text says. It says sin(30) is positive and sin(-30) is negative. They have the same magnitude but opposite signs.

[Anonymous No.7960804]

>>7960756

But the identity states -sin(30) = sin(-30).

[Anonymous No.7960808]

>>7960804
-sin(30) is negative

sin(-30) is negative

What's the problem?

[Anonymous No.7960812]

>>7960737
[eqn]\color{YellowGreen} { > \text{why iz } -f(x) \equiv f(-x) \text{? XDDD} }[/eqn]

[Anonymous No.7960813]

>>7960808

Damn. I've just wasted a bunch of time thinking that it's a lot more complicated than that.

[Anonymous No.7960843]

how do i find the formula for the distance an object falls in time time. when its dropped at 1000 feet, what is the time it takes the object to hit the ground and whats the velocity ( how do i find them? )

[Anonymous No.7960848]

>>7960843

D = 1/2gt^2


Rearrange for t.

[Anonymous No.7960853]

>>7960848
how do dat im autistic step by step sos i can learns plz

[Anonymous No.7960856]

>>7960853

Find a 1000 ft tall building and jump off. But wear a helmet with a go pro. No parachutes.

[Anonymous No.7960857]

>>7960848
isnt it 32 ft/s^2 or 16t^2
i got 16t^2; 5 sqrt 10/2 sec and 80sqrt10 ft/sec

[Anonymous No.7960935]

Can't find this explained well anywhere. Thales' theoremof triangle proportionality up in this bitch:

Why doesn't DC/AD=CE/BE? Is it because AB and DE aren't parallel? Why doesn't DC/EC=AD/BE work? How in the FUCK can I even know what goes and what doesn't? Help me out here please, I wont move on without learning this first.

[Anonymous No.7960965]

>>7960935
>Why doesn't DC/AD=CE/BE? Is it because AB and DE aren't parallel? Why doesn't DC/EC=AD/BE work? How in the FUCK can I even know what goes and what doesn't? Help me out here please, I wont move on without learning this first.
Anon, here's a tip.

When you're convinced of something you know to be false, write out exactly why you believe it is true. Seriously, try to post your justification of your thoughts here and I bet that midway through typing it, you'll find where you're wrong.

[Anonymous No.7961103]

>>7960423

[Anonymous No.7961156]

>>7960935
>>7960965
I just don't understand what is going on in the picture. How is this connected to triangle proportionality theorem? Theorem states that at least one line must be parallel. Here none are. Therefore I cannot even assume anything since I don't know how to work with this. Literally clueless. I understand normal rules don't apply here, but in what way can I compare the sides? Apparently CE/DC=AC/BC but I don't get it how.

[Anonymous No.7961166]

>>7961156
This could only work if...

[Anonymous No.7962912]

>>7956813
How do I plot functions of more than one variable on paper? To give a silly example, lets take f(x,y)=x^2 +y.

[Anonymous No.7963052]

Is there a way to make a direct relationship between slope and angle? Say you have the slope of 2 lines, can you know just with that info how much you would to rotate one of them so they're parallel?

[Anonymous No.7963503]

L'Hôpital's rule states that
[eqn]\frac{f(x)}{g(x)} = \frac{f'(x)}{g'(x)}[/eqn]
under certain conditions. And yes I know what those conditions are.

Is there an inverse of this rule? As in
[eqn]\frac{f(x)}{g(x)} = \frac{\int f(x) dx}{\int g(x) dx}[/eqn]
If so, what are the conditions required for it to hold?

[Anonymous No.7963519]

>>7963503
No, that's fucking stupid. Do you not see how nonsensical your second equation is?
L'Hopital's rule relies on the difference quotient at a specific point, i.e. local information, while the integral relies on global information.

[Anonymous No.7963534]

>>7963519
Alright, thanks, I think I got it.

[Anonymous No.7963544]

>>7963503
>[math]\frac{f(x)}{g(x)} = \frac{\int f(x) dx}{\int g(x) dx}[/math]
oh shit nigger what are you doing

[Anonymous No.7963560]

>>7963544
I don't know. I was hoping some inverse of L'Hôpital's rule existed. I guess not.

[Anonymous No.7963569]

>>7963560
Before asking this stufff on a chinese cartoon girl imageboard. Think to yourself this: "If an inverse of L'Hôpital's were to exist. What would it be used for and why?"

[Anonymous No.7963690]

>>7963560
>I was hoping some inverse of L'Hôpital's rule existed.
Naive. If we had shit that nice, life would be easy.

[Anonymous No.7963694]

do the stem majors here struggle with business classes like accounting? I'm struggling pretty hard.

[Anonymous No.7963697]

What's the point to calling monatomic molecules, "molecules"?

[Anonymous No.7963711]

>>7963694
>do the stem majors here struggle with business classes like accounting?
Shit tier college/uni, and hence student detected.

[Anonymous No.7963769]

>>7956813
that pic gave me cancer

>mfw my friends and family imagine lab work like that

[Anonymous No.7963788]

>>7956813
Using the matrix representations for the electron, I get the result from your class.

[Anonymous No.7963899]

>>7960737
Yes, 30 degrees is in the first quadrant, but where is -30 degrees?
How high are you?

[Anonymous No.7963960]

>>7963899
>How high are you?
Not sure if actual maths question or drug question.

[Anonymous No.7964357]

>>7963690
What do you think this thread is for m8

[Anonymous No.7964440]

Why are organic chemists so obsessed with dichloromethane? Is is a meme solvent?

[Anonymous No.7964450]

what degree should I major in and why?

no tim & eric tier answers that consist of, "follow your dreams"

[Anonymous No.7964452]

>>7964450
Mechatronics because you'll be the only STEM major with a job once everything is fully automated.

[Anonymous No.7964482]

>>7964440
It's fairly nonpolar and hydrophobic so you can use it to extract water insoluble salts by just dumping it in a sep funnel, shake it a few times and vent, wait for layers to settle, done.

[Anonymous No.7964822]

How does the the rest of the world teach math and science compared to the US?

[Anonymous No.7964931]

In most species runaway traits from sexual selection mostly manifest themselves on the male sex. How come the opposite is true for humans(women with large breast and buttocks)?

[Anonymous No.7965196]

>>7958015
Anyfam who can help with my problem (go back 2 replies)?

[Anonymous No.7965199]

>>7965196
...as in not the post I was replying to, but the one that one was replying to. Not two posts above.

[Anonymous No.7965400]

>>7956813
what is the speed of silence?

[Anonymous No.7965417]

is it B?

[Anonymous No.7965439]

>>7964931

https://en.m.wikipedia.org/wiki/ZW_sex-determination_system

http://learn.genetics.utah.edu/content/pigeons/sexlinkage/

Male birds get ZZ chromosomes, Female birds get ZW chromosomes.

Female humans get XX chromosomes, Male humans get XY chromosomes.

Z and X chromosomes have more genes than W and Y, also Z chromosomes control for feather and color type in sexual features.

Do you see the pattern here?

[Anonymous No.7965469]

I got provisionally admitted to a four year university in California for fall 2016 and I was wondering if I could still take classes for my major. Can I take a class in the summer and fall while taking classes at the four year university?

[Anonymous No.7965485]

>>7965417
Yes.

[Anonymous No.7965489]

>>7965469
*take community college classes for my major

[Anonymous No.7965505]

I am a white skinned male and my girlfriend is a brown skinned female. If we have a child what skin color will he or she have?

[Anonymous No.7965524]

How do you do this without knowing what distribution it is?

Tbh, I just assumed there are 8 rectangles and decided it's 1/8, but is there no more mathematical way to do it?

[Anonymous No.7965533]

>>7965524
1/2*base*height?

[Anonymous No.7965538]

>>7965533
Lol yeah I guess that works too. I was hoping for some way to solve it with statistics/probability rather than geometry

[Anonymous No.7965555]

>>7965538
you could define the probability as a piecewise function and then perform the necessary calculus on it, but you'd end up with the same result.

1/2 b h

[Anonymous No.7965556]

>>7965538
well, that is with statistics...
The area under the distribution from 30 to infinity is the probability of waiting that long, and since p is 0 for anything larger than 40 mins, then p = integral from 30 to 40 of -.0025x+.10

[Anonymous No.7965576]

>>7965555
I see now thanks. One question though -- where's that .10 in the integral coming from?

[Anonymous No.7965614]

>>7965576
The vertical shift. It goes to .025 by 30, so it must be .10 at 0.

[Anonymous No.7965762]

>>7964452
>not AI researcher

[Anonymous No.7965950]

>>7965485
It wasn't. Dunno why tho

[Anonymous No.7967015]

According to conservation of energy, energy cannot just dissappear, so where does the electricity in our brains dispense to when we die?

[Anonymous No.7967168]

I have to redo the students work correctly and outline two mistakes.

I've found them, but I'd like to double check.

The mistakes are in (ii) and (iii)

In (ii) he uses the cos of 42 instead of the sin

In (iii) he creates a rounding error by not using the full version of the length of AB.

If I'm wrong please do not tell me the answer.
Thanks.

[Anonymous No.7967187]

>>7967168

Just realized (iii) is not wrong. Using the full length of AB will still get 26 (to 2 s.f.).

[Anonymous No.7967253]

>>7967187

Okay guys, I can't find anymore errors other than the two mentioned.

Is (iii) considered an error?

Using the rounded figure for the length of AB gets a full figure of 25.87374457 for the angle of BAC.

Using the full figure of length AB gets a full figure of 25.702612 for angle BAC.

Both are 26 degrees to 2 s.f.

[Anonymous No.7967276]

>>7967168
>dat font
Holy fuck.

[Anonymous No.7967287]

>>7967253

And I think 26 must be correct. Because the three respective angles in the two smaller triangles (ABD and BDC) add up to 180 and the angles in the large triangle ABC also add up to 180.

[Anonymous No.7967553]

>>7967187

Can any of you clarify this

[Anonymous No.7967593]

I want to get a master's degree in math. I have a bachelor's degree in computer science and I graduated with a GPA of about 2.5. I'm planning on working as a software developer for a few years and studying math in my free time, then taking a semester of post-baccalaureate where I'll take some difficult senior-level math courses. If I do all of this and then knock the ball out of the park with the GRE, do you think I could get into a program that would be worth my time?

I don't want to get a doctorate because I am at high risk for suicide and I don't want to be a professor.

[Anonymous No.7967653]

>>7967593
someone got rused by /sci/

[Anonymous No.7967942]

>>7967653
I haven't come to /sci/ regularly in a few years. What are you trying to say?

[Anonymous No.7967983]

>>7967942
that there is no point in getting an MS in math unless you want to be a researcher or a teacher

[Anonymous No.7967988]

>>7967593
Why would you want to master degree? It's going to mean nothing for your career.

Just study the material you want in your spare time, you don't need to pay expensive course fees to learn something.

[Anonymous No.7968005]

>>7965950
What the fuck, why would it change anything whether it's written 0.5h and 1.0h or 30min and 60min ?
Tell your teacher s/he's retarded.

[Anonymous No.7968029]

>>7967983
>>7967988
Thanks famalam.

[Anonymous No.7968050]

>>7958131
Sure, why not.

[Anonymous No.7968051]

>>7956813
well you've got the formula right there
just work it out..
and look up the levi cevita symbol if you have to

[Anonymous No.7968122]

>>7967253
>>7967168


bump

[Anonymous No.7968127]

>watch first lecture of linear algebra uni course
>goes smoothly understand everything as you expect
>suddenly he starts talking about 9 dimension and 8 plane because 1 vector build on the other
y-yeah obviously doc
at least it's an interesting break from learning algos/datastructures and javascript meme frameworks

[Anonymous No.7968136]

Can anyone tell me why when getting a d' for hit rate vs. false alarms I end up with infinity when either the hit rate or false alarm rate is 1? I know it has something to do with Gaussian distributions but I don't really get why.

[Anonymous No.7968231]

>>7968127
Generalizing into arbitrary dimensions is like the whole point of linear algebra. It's easy when you view it as a matrix manipulation.

[Anonymous No.7968853]

So I was looking at past calc tests and came across pic related. I'm pretty sure I need to use induction to prove this question. I am easily able to prove the base case but get stuck after that. Any tips?

[Anonymous No.7968871]

>>7968853
What are you stuck on? It's just algebra.

[Anonymous No.7969150]

>>7968853
are you fugging retarded?

[Anonymous No.7969545]

>mfw people don't respond to my stupid questions

[Anonymous No.7969570]

>>7960253
>that moment when you remember complex numbers exist

[Anonymous No.7969575]

>stupid questions
Why am I a failure if muh IQ is 142?

[Anonymous No.7969694]

>>7967168
>>7967253

REEEEEEEEEE, come on faggots I have to hand it in soon. P-p-please.

[Anonymous No.7969776]

Can someone explain ANOVA to me under the assumption that I'm a retard, one step down from a literal monkeyman? I don't even know what it's supposed to tell me, like so what about the means, what, I don't

[Anonymous No.7969803]

>>7969694
> dat mass
shame about the donkey face tho

[Anonymous No.7969810]

>>7958071

this. like serious man what the fuck is she doing?

[Anonymous No.7969823]

>>7959144
>>7959144

no way in hell I'm PAYING to have some corporation have access to my DNA. I don't know what their "Terms & Conditions" are, but assuming they're like all corporations when it comes to personal data, they have free rights to do whatever with, and sell to whoever, the data that is resultant from your DNA.

no thanks.

[Anonymous No.7969890]

>>7969803

So can you confirm?

[Anonymous No.7969989]

How do I solve for t in e^(t-1)+t^2(2t^2 -3) < 0 I have no idea where to even start. I feel like an idiot not being able to do algebra and a stupid question.

[Anonymous No.7970040]

Can someone please provide me an infographic, diagram, or flow chart that explains tiers of learning for math?

A math professor in high school (I took summer classes) gave me a book on Galois Theory and I despaired. I couldn't understand it. I know that one needs to understand Modern/Abstract Algebra, but what are the prerequisites to understanding that or more particularly Galois Theory? It's been years since I've been in a math class, however, I wanted to autodidact this stuff and see how far I can get.

[Anonymous No.7970044]

Anybody has any idea what alloy has a curie temperature of 170 celsius, give or take 10 degrees.
can't find a good table with data on that shit

[Anonymous No.7970056]

Non native speaker here, which one is the correct term?

>for each tree we determined the percentage of bad apples per total apples

>for each tree we determined the percentage of bad apples of total apples

plz reply


pic more or less relatively related

[Anonymous No.7970062]

>>7970044
not sure if helpful

[Anonymous No.7970074]

>>7967015
neurons die fast. the gradients across the membrane that build the electric potential vanish because the cell membranes go to the dogs. the ions are still there, and they mix more or less, and without voltage, without seperated charges -> no electricity

[Anonymous No.7970085]

>>7970062
nothing really close to 170 C but thanks, i never thought a big list of that would be so hard to find, i found a big chem textbook that claim to have it, but it's behind 200$ paywall

[Anonymous No.7970112]

>>7970085
not sure if alloy

[Anonymous No.7970114]

>>7970085
plz reply to this: >>7970056

[Anonymous No.7970118]

>>7970112
I think i found it, closest match is a type of ferrite with grade of tsf-5000 sold by a company in illinois, but thanks for the tables guys.

[Anonymous No.7970128]

>>7970118
it was just me all the time. plz reply to this: >>7970056

[Anonymous No.7970132]

>>7970128
2 people near me and i agree that the first sentence sound much better

[Anonymous No.7970148]

>>7970040
Linear algebra, bilinear algebra and basics of abstract algebra, at least be familiar with group actions, polynomials and fields (duh). When you are done with that, start reading and you will see how you do.

[Anonymous No.7970204]

I'm going to go work out and then do some math and Physics and post any questions I have here

Ignore this M8s

[Anonymous No.7970226]

>>7967168
>>7967253

Can one of you fags confirm this. Come on, it must be a 15 second triviality for a typical /sci/ genius.

[Anonymous No.7970358]

>>7970056

I'd say:

>for each tree we determined the percentage of bad apples proportionate to the total amount of the apples.

[Anonymous No.7970749]

>>7956813
How the fuck do I wake up early everyday? I sleep through ALL my alarms, and it's ruining my study schedule.

[Anonymous No.7970783]

Help me out here

What are the best studies that aim for the future? As in, what studies do you think are the best for inventing/making/discovering the tech/facts/breakthroughs of tomorrow?

[Anonymous No.7970798]

>>7970749
Go to bed early or just dont sleep at all

[Anonymous No.7970823]

>>7970783
>As in, what studies do you think are the best for inventing/making/discovering the tech/facts/breakthroughs of tomorrow?
There will be breakthroughs in every field. What do you want to contribute to?

[Anonymous No.7970926]

http://m.eurostemcell.org/factsheet/embryonic-stem-cells-where-do-they-come-and-what-can-they-do

>It is not allowed to inject human cells back into blastocysts

And what would be the ramifications if it were allowed? What type of testing could be done, and could a wider range of diseases be cured?

What's the general consensus on how permissive bioethics laws should be around here?

[Anonymous No.7970945]

>>7968853
yes it's induction

https://proofwiki.org/wiki/Sum_of_Sequence_of_Cubes/Proof_by_Induction

[Anonymous No.7970951]

Is it common for IR values to not be EXACT? Do the surrounding atoms cause changes in the IR results?

I have a benzene that is """supposed""" to be 3000 cm-1, but it shows up as 2959 cm-1. I also have a N-H that is """supposed""" to be 3340 cm-1 but is 3291 cm-1. I know this is basic O-chem garbage but my OCD is being triggered

[Anonymous No.7970988]

>>7970823
Medicine or genetics is what i had hoped. Something close to home that is an issue now, rather than the universe and machines for example

[Anonymous No.7970998]

>>7956813
Is coffee good? I mean it keeps you active and all that, but i hear caffeine is bad. What is your evaluation?

[Anonymous No.7971036]

In my GR class my prof talked about finding the solution to Einstein's equation for a spherically symmetric body in vacuum. He then said that the ricci tensor vanishes.

I am a little confused about this point. Since we're in vacuum T_uv vanishes, but why does that necessarily mean that Ruv vanishes as well. Couldn't it be that Ruv - 1/2 guv R also happens to vanish for all components? Or is that simply impossible?

In summary, why does vacuum imply vanishing Ricci tensor?

[Anonymous No.7971101]

How do I know whether a set is in R^2, R^3 and so on?

[Anonymous No.7971147]

Hello fellow /sci/entists, I would like to know where I could get this book "Geometry by Harold R. Jacobs", anyone know any good sites on webs that would have this as a pdf, my searches yielded no result...

Thanks!

[Anonymous No.7971236]

>>7970951
Remember the IR spectrum is just the range of light frequencies absorbed by different structural features. You'd expect a functional group to behave somewhat differently depending on overall structure and electronic environment.

Just think of IR as a qualitative test unless you're going full pchem or want to specialize in spectroscopy. Exact predictions are not trivial

[Shaun Grimes No.7971778]

>>7971147
bookzz dot org

[Forrest Mcconnell No.7971781]

>>7971101
the number of components?

but it's hard to say without more info
why are you asking the question?
what sort of problema re you going?
what are you given in the problem and why do you need to know if it's in R2 or R3?

[Deloris Hicks No.7972025]

>>7956813
I'm wondering why exactly in BCC materials strain rate affects the brittle-to-ductile transition temperature. Could any anon try to explain this in relatively simple terms?

Thank you

[Fredrick Mills No.7972754]

I need to find the fourier coefficient of a signal but I'm not sure what to do with the complex answer. Do I just take the real? Amplitude?

[Shelly Graves No.7972892]

What happened here?

Why did the first 12^k turn into a 1+?

[Michelle Larsen No.7972946]

>>7972025
Less (or more) slip planes?

You doing something with charpy impact testing?

[Beatrice Crane No.7973294]

how do i become a good student

[Anonymous No.7973408]

Can any point me in the right direction? Or explain to me how the coefficient in the equation for a circle effects the graph?

Ex. (x^2)+(y^2)=16 (I know that this is circle with the center at the origin worh radius of 4)
But how does this differ (x^2)+(4y^2)=16

The question is how do I graph this without a calculator and how does the coefficient change the graph?

[yolo No.7973551]

/sci/, I'm having trouble with non-disjoint cycles.

here's an example:

(1 2 3)(2 4 5)(2 6 4 5) = (1 5 6 4 2 3)

I did this last year and I'm revising all my group theory stuff for an assignment, but I can't remember how to get from LHS to RHS.

All my online lecture notes just have the answer written under with no explanation (the lecturer showed us how in the lectures but I can't remember how it was done)

[yolo No.7973558]

>>7973551
Just figured it out, feel stupid for not knowing how simple it is... -.-'

[Anonymous No.7973636]

>>7971778
Danks bro. Found the book.

[Anonymous No.7974648]

Can someone tell me the formula for the power series of the complete eliptic integral of the second kind?

[Anonymous No.7974704]

So. Quarks. How the fuck does a force increase in strength with increasing distance?

[Anonymous No.7974712]

don't think engineering is for me lads

[Anonymous No.7974882]

Why do I get a different standard deviation with ANOVA than I get with regression?
I need somebody to explain it to me like I'm a retard, because I am.

[Anonymous No.7975145]

What would be the best way to factor a 3rd degree polynomial with a non integer root and two complex roots? (aka discarding synthetic division)

[Anonymous No.7975157]

I'm trying to derive a formula to determine prime numbers based on their index - ie the 3rd prime is 5, the 5th prime is 11, so on.

Any pointers? Besides "give up, you're wasting your time"

[Anonymous No.7975158]

>>7974712
That not something an engineer would prod with a 10 foot pole

[Anonymous No.7975164]

>>7975157
>Any pointers?
0x3A28213a
0x6339392c
0x73632e

[Anonymous No.7975171]

>>7975164
kek

[Anonymous No.7975178]

What is a linear algebra question referencing by 'M22'?

[Anonymous No.7975182]

>>7975164
I really should know better by now.

[Anonymous No.7975377]

If wounds caused by sharp knives heal slower, why are scalpels so sharp?

[Anonymous No.7975849]

Can you get AIDS from giving yourself a blow job?

[Anonymous No.7975859]

>>7975377
Unfortunately you have a very good point.

[Anonymous No.7975946]

What is a plank instant? I think I read on here before that it doesn't necessarily describe an actual measure of time (though the wiki just states that it's the time that it takes light to cross a Planck length).

Am I just misunderstanding?

[Anonymous No.7976057]

Is the galaxy moving? I know it spins but does the whole thing move like in a direction and if so how fast?

[Anonymous No.7976067]

>>7975946
What's a meter? Just some arbitrarily defined unit length. It's not any more significant than this. It's just a really short time scale. For instance, you wouldn't measure the distance to the grocery store in inches, which is why you would decide to introduce the unit of miles so that your numbers are not as cumbersome. That's it.

[Anonymous No.7976144]

Is there a general way to find an explicit n-th formula for a recursive sequence?
I remember it's possible with eigenvectors, but I have absolutely no idea how.

Specifically, it's f(n) = f(n-1) + 2f(n-2)

[Anonymous No.7976159]

How do I relate the derivative of the entropy and the derivative of a volume in a photon gas? (dS/dV or otherwise).

I can't seem to make it work.

[Anonymous No.7976207]

I have a knife that I suddenly found out the tip and the middle are magnetic and only those parts, they were not before and I have no clue how this happened, anyone explain it to me?

[Anonymous No.7976231]

I am trying to design a circuit that will completely turn off the Powerboost 500 (by connecting the ground and EN pins) automatically. As part of this, I have come up with the attached circuit. I have very little experience with electronics, but my reasoning is as follows:

When the battery is first connected, the EN pin will be grounded and no current will flow. Upon pressing the button, current will begin to flow and the transistor will be inhibited, so the device will continue to operate.

If this circuit works as I expect, I will add a microcontroller between the transistor and 5V pins, allowing me to cut power automatically when a certain event is triggered. This will require pressing the button again to turn on the circuit.


More info: https://learn.adafruit.com/downloads/pdf/adafruit-powerboost.pdf

[Anonymous No.7976663]

Is entering a Ph.D. program at the ripe ol' age of 30 pants on head retarded? I want to get a maths doctorate and it seems like it's possible to be finished in 5 years. I don't really care what my dissertation is about so I can just research some shitty trivial problem.

[Anonymous No.7976692]

Is a sequence of all terms the same, monotone increasing and decreasing (but not strictly.) Or is it simply not monotonic? I.e. define a sequence to be just infinite 1's.

[Anonymous No.7976694]

>>7976663
Do you really want a PhD in mathematics just for the sake of it?

[Anonymous No.7976712]

>>7976692
Depends on your definitions. Under the definitions I was taught, an infinite sequence of ones would be monotonous. But it's very probable that definitions vary in this case between schools/lecturers/books.

[Anonymous No.7976728]

I'm interested in reviewing my knowledge of math from the bottom up.
Can I use a roadmap like this:
http://hbpms.blogspot.com/
and go through each topic without confusion, or would you consider the ordering of the topics to be conflicting?

[Anonymous No.7976733]

>>7976712
it fits the definition we use of monotone increasing and decreasing, i.e. n+1>=n &n+1<=n. but not strictly monotone increasing and decreasing: n+1>n & n+1<n ( where n is nth and n+1th term)

[Anonymous No.7976746]

My friend rested a cigarette on the top of a lighter. It exploded after a while and was covered with ice.

The fuck happened?

[Anonymous No.7976789]

>>7976694
Hint: you don't, and you won't even finish if you manage to get in somewhere.

[Anonymous No.7976792]

>>7976746
PV = NRT m8

[Anonymous No.7976796]

>>7976792
>mfw high school physics
>mfw "practical" physics
>mfw the only thing I remember about gases is that they're smelly and they don't really impress girls no matter how impressive they actually are

[Anonymous No.7976851]

Let's say that a rogue satellite somewhere around the size of Titania or Oberon falls into earth's gravitational pull, and starts orbiting us at 500,000 miles --twice the distance of the moon. What would happen? Would the tides change/ how would the moon and earth's orbit be affected

[Anonymous No.7976858]

Why is it that if I scratch/ pinch myself in one area on my back I automatically feel another pinching feeling somewhere else on my back?

[Anonymous No.7976861]

>>7976796
>
That's actually chemistry mate. Basically the cigarette exploded it but as the gas suddenly expanded and volume it had a short drop in pressure that exceeded the volume change. In order to accommodate this as N and R remain constant T shrank very low. Then the gas mixed with enough air to become combustible and the cigarette tip caused it to explode. But the temperature change was so great that the brief increase in heat didn't transfer enough energy t reheat it.

At least that's what i think but I'm a stoned chemist.

[Anonymous No.7977052]

>>7976694
>>7976789
Not for the sake of it. I want to become a mathematician, but I don't want to become a professor, partly since it's so unlikely. I want to enter industry, something like finance (inb4 hurr durr /sci/ meme) or machine learning. Since I don't want to become a professor, I don't need to write a stellar dissertation.

In short, I'm curious as to whether it is possible to get a doctorate in 5 years.

[Anonymous No.7977054]

>>7975158
Considering that's a homework question in my semiconductor physics class, yes it is

[Anonymous No.7977119]

>>7968005
Given the same x-axis you'd get a flatter but wider area, given it'd still be 1 a.u.

[Anonymous No.7978399]

Currently taking gen chem 2. Have little recollection of gen chem 1. Failed first test horribly. Second test is on Chemical Kinetics, Chemical Equilibrium and Chemical Equillibria: Acids and bases. What prior knowledge do I need to understand these chapters. Text is McMurray Fay Chemistry.>>7978396

[Anonymous No.7978433]

>>7978399
Just do all the problems at the ends of those sections senpai. Chemistry is easy, there is just a lot of it so you have to put in the hours. You can do it if you try senpai.

[Anonymous No.7978443]

OK, my question is really simple.

Equation 1.17 in Physical Chemistry: A Molecular Approach.

I did the math and found the equation is r^3, not r which is stated. So someone please explain that to me.

[Anonymous No.7978542]

So our professor was absent and left us with bookwork. Trouble is our book is garbage at explaining things.

I am doing 18.4 right now in this picture. How should I begin this sort of problem?

[Anonymous No.7978735]

>>7976746
it's an old bar joke. a prepared cigarette.

[Anonymous No.7978737]

>>7978433
Thank you sensei. Your words have encouraged me.

[Anonymous No.7978742]

>>7970926
well the british do a lot of unethical research already

[Anonymous No.7978862]

>>>/qa/487575
Is Tits Group Nice Group?

:3

[Anonymous No.7979220]

What is the formula for finding DX/dy of x^x

[Anonymous No.7979272]

>>7964822
exactly the same

[Anonymous No.7979282]

>>7979220
apply the logarithm to the equation, then the exponential and derivate

[Anonymous No.7979317]

Can anyone see how the complex unit j is removed from the denominator?

I know that the two exponentials subtracted and divided by two are reduced to sin of the angle (Eulers theorem)

[math] e^{j \theta} - e^{-j \theta} = \frac{sin(\theta)}{2} [\math]

The thing is that if I apply that rule I end up with the following:

[math] \frac{A}{T} * [ \frac{sin(\frac{m*\pi*t}{T})}{j*m*\frac{\pi}{T}} [\math]

Thus I still need to get rid og the complex j in the denominator. I can only think of performing a complex conjugation, but this will result in sin squared etc. which isn't in the end result of the answer, pic related.

Any help would be gratefull if someone thinks of something hit me up!

[Anonymous No.7979323]

>>7979317
kek latex fail, redo version:

Can anyone see how the complex unit j is removed from the denominator?

I know that the two exponentials subtracted and divided by two are reduced to sin of the angle (Eulers theorem)

[math] e^{j \theta} - e^{-j \theta} = \frac{sin(\theta)}{2} [/math]

The thing is that if I apply that rule I end up with the following:

[math] \frac{A}{T} * [ \frac{sin(\frac{m*\pi*t}{T})}{j*m*\frac{\pi}{T}} [/math]

Thus I still need to get rid og the complex j in the denominator. I can only think of performing a complex conjugation, but this will result in sin squared etc. which isn't in the end result of the answer, pic related.

Any help would be gratefull if someone thinks of something hit me up!

[Anonymous No.7979347]

>>7979317
>>7979323
https://www.wolframalpha.com/input/?i=e^%28it%29-e^%28-it%29

[Anonymous No.7979360]

>>7979347
What's your point? I already stated how the exponentials cancel out and become a sine over 2.

I'm trying to get rid of the complex unit in the denominator while getting the same result as the pic.

[Anonymous No.7979367]

>>7979347
>>7979360
Fuck me I'm a retard, just noticed the two exponentials cancel out and become sine over 2 J <- Complex

Thanks anon

[Anonymous No.7979622]

my school offers a course in actuarial probability

how much math should i know before going in and how should i prep myself for it?

[Anonymous No.7979629]

Just started multivariable calculus and I missed a lecture and don't know the fuck I'm doing. Send help.

[Anonymous No.7979831]

About Double-slit experiment

why wont the marbles behave exactly the same as the electrons if they aren't observed by any one/anything?

[Anonymous No.7980175]

>>7978443
Since nobody wants to download the book in the wiki.... I'll post pictures.

[Anonymous No.7980176]

>>7980175

[Anonymous No.7980178]

>>7980176

[Anonymous No.7980287]

>>7974704
Try pulling apart magnets

[Anonymous No.7980294]

>>7979629
Find equation of line which through both points are found, which gives you a parametric equation, x=t+1, y=t, z=2+t.

[Anonymous No.7981628]

>>7980294
Thanks my man

[Anonymous No.7981696]

I'm not quite educated enough to refute one of these flat-earth arguments - a common one is that in certain places when you look across a certain size lake, you shouldn't be able to see the city on the other side because the curvature would conceal it.

The only explanation I've seen is that when you see the city across the water, it's a mirage caused by the air temperatures or something? I live near one of these places though and I see it all the time.

[Anonymous No.7982568]

Okay, so I know that 9 mod 6 = 3 because 3 is the remainder of 9/6. But what happens when it's 6 mod 9?

[Anonymous No.7983724]

Can someone apply tree structure rules to decompose the phrase:
The root Z[x] monic that are rational are integers?
If the purse of a yellow cat is blue then it's cheap.

[Anonymous No.7983727]

>>7983724
Please ignore the second phrase about roots.

[Anonymous No.7983739]

>>7982568
What's the remainder when you divide 6 by 9? it's six

[Anonymous No.7984077]

6 = 0 * 9 + 6

[Anonymous No.7984291]

Help me /sci/, any easy way to memorize TCA cycle?

[Anonymous No.7984351]

what chemistry book should I read if I want to make some amphetamine? for my own personal use
I know some chemistry basics but I need to be sure that I'm not gonna poison myself
could you give me some direction of my education here?

[Anonymous No.7984490]

After the classes I try to read the textbook's section on the subject given, but I feel like I waste too many hours reading.
I'm thinking in skipping right to the problems of the book, but I don't know if it is the most effective way to study.
How do you do it?

[Anonymous No.7984555]

>>7984490
Jump straight to problems, do the ones you can and go back to reading for the ones you can't.

[Anonymous No.7984724]

reposting this from the other SQT because I'm fishing for opinions

>be CS major
>good at high level math
>understand Graph Theory pretty well and other initially esoteric CS subjects
>awful at programming such data structures
>getting increasingly decent and more skilled at working with machine code and building assemblers in C
Am I going to be fucked if I try to enter a CS doctorate's program without being able to program theoretical data structures well? I've heard that analysis == grad school whereas compiler-building == industry

I also think a large part of the issue might be because I'm trying to do it in Java, but that can't be helped much. It's just starting to worry me because I make near perfect scores on the written exams but make B/Cs on the programming labs

[Anonymous No.7984732]

>>7984724
>graph theory
>initially esoteric

cute

[Anonymous No.7984736]

>>7984732
It was an assumption on the behalf of my classmates. I knew about Graph Theory already because I took those math courses way before I got into the theory-heavy CS courses

[Anonymous No.7984740]

>>7984736
i was just being a cocksucker trying to imbue others with my own insecurity

/sci/

[Anonymous No.7985345]

>>7976144
It goes somewhat like this:
[math]
F^n = \begin{pmatrix}
f(n) \\ f(n-1)
\end{pmatrix}
=
\begin{pmatrix}
1 & 2\\
1 & 0
\end{pmatrix}
\begin{pmatrix}
f(n-1)\\f(n-2)
\end{pmatrix}
[/math]

[math]
= AF^{n-1}=A^2F^{n-2}=...=A^{n-1}F^1=
A^{n-1}
\begin{pmatrix}
f(1)\\f(0)

\end{pmatrix}
[/math]

To calculate powers of A now, you need to find it's eigenvalues and vectors and do a transformation

[Anonymous No.7986672]

spivak or apostol?

actually I got pretty good deals, so I bought both, but I'm curious what you guys think of them. I've already spent some time with spivak, but it's fucking hard because I always feel like I'm missing something. I'm familiar with proofs, and I enjoy them/ find them easy in predicate logic. But when numbers get added in I can't handle them anymore (although when I check the answer I kick myself for it being so obvious). I just wanna have a competency in maths

[Anonymous No.7986691]

>>7978399
>2016
>not just solving for units

Jesus I feel bad for you fuckers.

[Anonymous No.7986692]

>>7986672
>so I bought both
I don't understand -- just read both then. There's no reason to only get one viewpoint on the subject if you own two books.

[Anonymous No.7986703]

I'm trying to teach myself elementary differential equations and I'm brushing up on my Calc 1-3. I'm about half way through Calc II. Do I actually need to go to calc 3 to understand diff eqs? I feel like I actually remember a majority of my calculus though it's a been a few years since I graduated.

Also I never really learned how to do physics. Is there any good place to learn?

[Anonymous No.7986729]

>>7986692
That's the plan, of course. I'm interested in /sci/'s opinions of the books though; maybe there's one I should read first or I should look out for something, etc. From other discussions I've read it seems like Apostol lays stuff out for the reader, while Spivak goes deeper and leaves a lot up to the reader. I'm concerned that if I study Apostol first, it will ruin some of the genuine 'aha' moments I might otherwise have if I just white-knuckle it on Spivak.

[Anonymous No.7986832]

Is First Order Mathematical Logic hard or am I just dumb?

[Anonymous No.7986915]

I think I may be retarded.

I need help deciding if the phrase "50% of all programmers know C++" is supposed to be P( C++ | Programmer ) or if it should just be P( C++ ) since it's over all programmers.

The reason I think it's P( C++ | Programmers ) is because later in the question it states "1% of all programmers work for Macrosoft."