/sqt/ - Stupid Question Thread: Urschel Edition

learn to read brainlet

literally the sentence before that section
>where, atan2 is a two-argument inverse tangent.

en.wikipedia.org/wiki/Atan2

K>=S>=1.

Where should I start at proving this? I'm supposed to use generating functions.

OK, this is probably a really dumb question, but I've always wondered this.

If the definition of work/energy in physics is force through a distance, how come my arms get tired when I hold a weight above my head? I'm applying a force to it, to stop it falling down, but I'm actually not imparting any work/energy onto it.

So why do I get tired/warm/etc. which would be signs of work being done?

The energy of the weight does not change, but it takes energy to keep the weight in it's state.

How can I prove the Riemann hypothesis and bench 700 lbs at the same time

>tfw 19 and organic chemistry is raping my ass

How relevant is this shit as a retail or hospital pharmacist? Is Organic II harder or just more coverage of the same topics?

The stuff you are holding is constantly moving downwards. Your arms cause an instantenous reactionary movement upwards, combined they are close to doing nothing at all, but the work done by your arms is real.

that's not real... right?

How do you do p-value testing for least squares method?

>Are nootropics a meme?
probably. I tried them and didn't notice any difference

What is the name for Sierpinski triangle for decimal?
How may I name it if I find something noone knows?
How do I find out if something is known or not?
Doesn't science keep an accurate register for everything?
How do I find a database where all abecedaria are kept?
If such things do not exist how do I create them? Let us create them!

Organic chemistry is the basis of all of Pharmacy. I am unsure what you are learning now, but understanding the structure of compounds is key to understanding how they work. In retail pharmacy you need that type of knowledge to understand interactions mostly. It also helps to understand things like stability. In the hospital pharmacy it is especially important to understand shit like solubility for IV-bags, because precipitation can kill people. An example my professors used is that adding 2 compounds into 1 IV bag is knowledge the pharmacist should have
tldr: Yes, it is important to know for stuff like product stability mostly and for more advanced Organic Chemistry, which is bonding of molecules in proteins and that type of thing. Spoiler: that is about the hardest thing you will learn

It is.
>PM has long been known for its typographical complexity. Famously, several hundred pages are required in PM to prove the validity of the proposition 1+1=2.
Math was a bit different before Gödel put an end to stuff like this. Even in all its futility, trying to achieve the fundamental goals of PM is quite romantic, and going that far makes me tip my imaginary fedora.

How to do refrain from guessing and checking math problems ? When i'm solving a integral for example i'm always thinking: ''this is probably wrong, lets just scribble something down and check how the professor solved it'' It's very hard to not do it this way as i have developed it as a way to not feel lost. I tend to get very surprised when i do things the correct way.

>PM

"It purports to reveal the fundamental basis for arithmetic. However, it is our everyday arithmetical practices such as counting which are fundamental; for if a persistent discrepancy arose between counting and Principia, this would be treated as evidence of an error in Principia (e.g., that Principia did not characterise numbers or addition correctly), not as evidence of an error in everyday counting."

"The calculating methods in Principia can only be used in practice with very small numbers. To calculate using large numbers (e.g., billions), the formulae would become too long, and some short-cut method would have to be used, which would no doubt rely on everyday techniques such as counting (or else on non-fundamental and hence questionable methods such as induction). So again Principia depends on everyday techniques, not vice versa."

Sounds like a self-esteem problem, not a math problem.

However, if you're actually incapable of solving integrals without checking, just isolate yourself from anything that will give you the solutions, such as the textbook, lecture notes, computer, calculator, and try to solve them on your own. See how many you can do, or get approximate answers for without "feeling" like you need to check. If you're still uneasy about that, think about other kinds of problems you don't need to check the answers to because you know how to solve them. What makes your method of solving them different from integrals? What is your reasoning? Can you apply the same reasoning to integrals?

In general, math is not a social activity and you shouldn't need to check other people's answers to "know" if yours is right. You should be able to verify it independently by deduction. That's kind of the whole point.

I need to calculate how many books each customer has bought and how many times each book has been bought, given this customer id and book that they bought, The language I am using is Prolog. Any help would be nice.

It would be amazing if i were able to see that my answers were wrong on my own related to finals etc.
I do enjoy solving integrals. They feel complex at my level and i feel smart when i'm able to solve them. Integrals feels different compared to other things. It's like a puzzle with many solutions that leads to the same answer.
Anyway, i will take your suggestion to hearth.

hey guys, i came across a really stupid problem but i couldn't solve it on my own...
i want to create a computer algorithm to solve a problem me and my friends came across by playing an online RPG.
but i have a math problem which is:

a player can throw 1 to 10 ten sided dices (1d10), lets say he throw 5 dices and get these results:

2, 5, 9, 10, 6

each 10 is one success, so lets remove it, (here comes the tricky part):

2, 5, 9, 6

now we need the optimal way to sum a pair of numbers to get another 10:
these are the possibilities to get another 10:
2 + 9; (*)
5+9;
6+9;

* being the optimal way, because removing the 2 numbers (one success):

5, 6 = 5 + 6
another success

i'm not sure you guys understood what i meant, my english is terrible.
But basically:
after checking for 10s and counting them, i need an optimized way to sum 2 numbers and check if they're >=10; if they're not then check the sum of 3+ numbers

Why has no one ever found a comet

Can I get some help with pic related?

I know I have to do some manipulation here in order to get the result of 200.

But I dont understand how, I already did everything. Once the switch is closed then the capacitor behaves as a short. So I merge 20k and 80k and get a voltage of ... 120?

Why is the answer 200?

v(0) is the cap fully charged so it has the same voltage as the cap being OC across the resistor.

Calculate the voltage and voltage divider:
[7.5*(70||80)]*[50/70]=200V

is the truncus symphaticus the same as the ganglions of the spinalnerve?

Do Magnets Work in Space With No Magnetic force taking place

My question has to do with the concept of dimension or "direction in space", more specifically, when considering a linear system as a system of equations compared to a linear combination of vectors.

I guess specifically what I'm curious about is, given an arbitrary linear system, why is the concept of direction in space sort of contained / stored in the variables when considering the system as linear equations, but then is stored in the vectors when considering the same system as a linear combination of vectors?

I know its sort of a strange question, so I'll phrase it using a more concrete yet still general example. Consider a linear system of three equations in three variables, where each equation is of the form (a_i)x + (b_i)y + (c_i)z = d_i. For convenience, and so that we may get some nice geometric intuition, suppose also they represent three distinct planes in R^3 (so we have linear independence). In the context of the system representing planes in space, it seems to me that dimension/direction is sort of "stored" in the variables x, y and z. Now this same system of 3 equations in 3 unknowns can also be expressed as a linear combination of vectors: x + y + z. Here direction of course is stored in the vectors themselves; the three variables that stored direction in the context of linear equations now simply scale the vectors.

And it gets even more bizarre when you consider that, considering the system as linear equations of planes in R^3, we can express each plane as a vector equation by dotting any vector parallel to it with the normal and setting it equal to zero!

And I suppose I'm also curious as to how this relates to the system when considered as a matrix / linear transformation.

Any stats people in here ?

The really good question!
This stands for useful and total work. You see, when car is moving it consumes gasoline and when it stands on the ground with working engine its still consume gas. So your muscles does.

What's the name of the theorem that states for all a and b in the Reals there exists an m such that ma>b

i've seen it called the archimedian principle:
en.wikipedia.org/wiki/Archimedean_property

So I'm supposed to prove this formula for vectors in pic related, and I can't find anything like it in the calculus books or the internet, does this ring a bell to any of you? I really need a hint :(

en.wikipedia.org/wiki/Dot_product#Geometric_definition

In regards to modular exponentiation by squaring and functions that implement it, why is it when the exponent is small, e.g. 2, it's slower than simply taking [math]x^2 mod (n)[/math]? This appears to hold true for exponents 3, 4, and maybe more.

Does anyone know how to prepare bacterial DNA for pcr? I'm an undergraduate and I'm trying to learn new methods.

I haven't had the chance to do much research into different methods because I'm out of my home country at the moment but the graduate student in my lab is seriously useless when it comes to learning new techniques.

TlDR: how do you extract DNA from bacterial colones for pcr.

Why is
10000/x + 15000/x^2 + 20000/x^3=40406 X=1.05
But
45000/x^6 = 40406 X=1.018
Why are they not the same?

Of course they are not the same since you add them together and not multiply them together. I am legit retarded. Anyhow how do I count?
10000/x + 15000/x^2 + 20000/x^3=40406

>Is [anything Joe Rogan has talked about] a meme
Always yes

The fuck am I doing wrong?

Bit confused, anyone want to elaborate?

For a) I wrote that L' = {b^n c | n >= 0} and the connection is that L' would be a subset and a possible substring of L

for b) I wrote L = {c, c^m b | m,n >=1} and the connection is that L' is not necessarily a direct substring of L, but still a possible subset of strings from L.

c) Would I draw a FSM (dfa/nfa) for L' ? So id how do I draw a dfa for a non specific language? L subset {b, c}*

So given the stochastic variable Y=X^2

The cumulative distribution
G(y) = P(X^2 \le y) = P(|X| \le sqrt(y) )

where do I go from here? I realize I suck at inequalities. My first thought was that X is less than sqrt(y) or X is less than -sqrt(y), but that does not sound right, as or becomes union with probabilities, and the union of ``less than sqrt(y)" and ``less than -sqrt(y)''

what are the steps in between the above that leads to:

P(-sqrty(y) \le X \le sqrt(y)) ?

Are knots just a sequences of infinitesimally small vectors?
Are categories just generalized groups?
Are groups just closure tests?
Are sets just containers?

Is it physically possible to completely remove all of the water in a toilet bowl using only a hairdryer?

Yes as long as you don't flush and refill the bowl.

it should evaporate if you just leave it there too, right?

I had a cup of water in my room that over the course of a few weeks or month/two, I forgot completely evaporated leaving only a bunch of gross looking dust left

>Are categories just generalized groups?
no, but groupoids might be interesting for you
en.wikipedia.org/wiki/Groupoid

>Are groups just closure tests?
no, groups measure symmetry

>groups measure symmetry

right, that's what I said, closure tests.

>partial function has one of the barbs missing from the arrow

that's cute

categories are generalized mathematical structures. That's their whole point, they generalise a bunch of different branches.

>generalized mathematical structure

IMHO categories aren't really general enough. I don't see what all the fuss is about.

orgo II was easier imo

I HATE THAT MOTHERFUCKER DELTE THIS

a)L' is empty, all words in L contain a
b)L' doesn't contain "c", since m,n>=1
c)Consider the language K={b,c}*
It is obviously regular. Intersection of regular languages is regular. L' is the intersection of L and K and therefore is regular.

Sorry, wouldn't b) be L' = {c^m b | m >= 1} ? Don't quite get why it L' cannot have any c's, since a^n c contains a's the entire subset should be omitted but c^m b should be fine ?

There are plenty of protocols online bro. Most require using detergent to lyse the cell, the separate the DNA, lots of centrifuging and heating, finally staining it with ethidium bromide. It's been years so I don't really remember, but this is something you can simply google.

Is this the correct antiderivative of 1/ (1 - sec(x))?

cot(x) + csc(x) - x?

Here's what I did:
∫dx/ (1 - sec(x))
∫[1 + sec(x) ] dx / [1 - sec^2(x)]
- ∫[1 + sec(x) ] dx / [tan^2 (x) ]
- ∫ cot^2(x) + cot * csc (x) dx
- ∫ (csc^2(x) -1) dx - ∫cot (x) * csc(x) dx
cot(x) - x + csc(x)

Why is burning 'fossil fuels' bad? People say it releases carbon but it had to be in the atmosphere before being absorbed by the biomass and compressed into coal. What is wrong with restoring the atmosphere? Life adapted before, it can adapt again. Let's bring back the Jurassic period.

I can't tell if you're being obtuse or not, but I'm going to give you the benefit of the doubt

The amount of CO2 and other noxious gases we're releasing is at an unprecedented pace/scale compared to what historically has happened before. organisms have been naturally selected to adapt to a specific environment, and man-made technological progress threatens to upset this balance. We are not giving the ecosystems/biomes enough time to adapt properly.

Think of it this way: You have a house by the shore. Sure, it may be a bit waterproof, but it won't be able to stand up to a tsunami.

There's also a bunch of related phenomena that comes with the burning of fossil fuels. You've probably heard of the greenhouse effect, which is the trapping of Earth's heat by the atmosphere. Without the GE, Earth would be at -30°C, so we do need some of the GE to keep us alive. However, due to the CO2, Methane, and other Greenhouse Gases, scientists and (sane) policy advisors predict a best-case scenario average increase in temperature of 2°C, which doesn't seem like a lot, but you have to keep in mind that this is an *average* change. Some areas will get warmer, and some will get colder, meaning more extreme temperatures in climates all around, which would absolutely destroy agrarian economies and developing nations, who bear much of the brunt of industrialization from other countries.

Hope my little harangue cleared some things up.

>I can't tell if you're being obtuse or not
Nope, just retarded. Thanks.

What were the first/earlier indications that the climate is changing?

>Nope, just retarded. Thanks.
Nah, man... Don't sweat it. I've just hung around here enough to the point I can't tell when someone's being ironic for the sake of being edgy sometimes.

I'd be happy to point you in the direction of useful climate change readings / policy stuff if you'd like

There have been signs for a long time, please just go to bed. Lets all get some rest.

I just wanted to know the first sign that spurred on all the research

And I just woke up, why would I go to bed?

>why would I go to bed?
Because you need to sleep more

don't quote me on this, but I think it was research in the Arctic that first may have tipped people off...

>From the late 1970s and through the 1980s, Exxon funded internal and university collaborations, broadly in line with the developing public scientific approach, and developed a reputation for expertise in atmospheric carbon dioxide.[1] Between the 1970s and 2015, Exxon and ExxonMobil researchers and academic collaborators published dozens of research papers generally supporting the "emerging consensus that fossil fuel emissions could pose risks for society" and exploring "the extent of the risks."
>In the late 1980s, Exxon became a leader in climate change denial.[27][28] Lee Raymond, Exxon and ExxonMobil chief executive officer from 1993 to 2006, was one of the most outspoken executives in the United States against regulation to curtail global warming,

The fact that the climate changes has been known for so long that it would be impossible to identify when this was first noted.

The thing about climate is that it takes significant effort to distinguish actual change from statistical noise (i.e. a run of consecutive warmer/colder-than-average years).

With regard to carbon-driven AGW, it's more a case of it starting with the observation that it "should" be happening (a consequence of the absorption spectrum of CO2 and the fact that we've spent the past century scouring the earth for sequestered carbon then putting it back into the atmosphere as fast as we can find it), then trying to analyse the extent to which this is apparent in the available data.

IIRC, the theoretical argument was first made around the middle of the 20th century. Since then, it's largely been a case of analysing weak indicators (tree rings, ice cores, etc) to compensate for the fact that systematic weather observations don't go back far enough to reliably separate trend from noise.

How do I prove that 0 is not actually a number?

The generating function of the left side should be written as a product of two generating functions (each containing just one of those binomial terms).

>how do I count?
>10000/x + 15000/x^2 + 20000/x^3=40406
Please help a retard that has forgotten basic math out. Why is it different from 45000/x^6?40406

Where can I find good courses about compsci like MIT OCW and (RIP) Berkeley's YT Channel?
No bully

Please help!

I'm dumb and don't understand statistics. I have a homework assignment due asap and I can't figure this one thing out, can you please see image related and quickly scribble down answers + work?? you'd be really helping a brother out....

You can divide by a number and get another number. When I divide by zero, my calculator says "not a number", therefore zero is not a number.

>I guess specifically what I'm curious about is, given an arbitrary linear system, why is the concept of direction in space sort of contained / stored in the variables when considering the system as linear equations, but then is stored in the vectors when considering the same system as a linear combination of vectors?

I dont really understand your question.
In both cases it is exactly the same, where is the difference?

You can restate the question to the solution of a system of linear equations to the linear combination of a vectorspace.
That means:
(a_1)x + (b_1)y = d_1
(a_2)x + (b_2)y = d_2

Can be trivially restated as:
(a_1,a_2)^T*x+(b_1,b_2)^T*y=(d_1,d_2)^T

Basically you are "taking the x out of each component of the vector".

The vectors in both cases represent the exact same thing.

>And I suppose I'm also curious as to how this relates to the system when considered as a matrix / linear transformation.
It is just the same. Roughly speaking each vector of a matrix represents a base vector in a vector space.

In that interpretation matrix vector multiplication becomes transforming the vector into another vector in a different vector space.

And solving a system of equations or asking whether a linear combination exists such that target vector is a part of the vector space, (which are the exact same thing) becomes the question whether the linear transformation contains the target vector in its image.

I am sorry if I am not answering your question, but I dont really understand where exactly your question it.

Wait... what don't you understand about this? This seems pretty self-explanatory to me (simply plug in X, solve for Y)

Just put 2 instead of x and solve for y^

I can't do that, my calculator only says "divide by zero error"...

I should get a better calculator

> When I divide by zero, my calculator says "not a number", therefore zero is not a number.

The standard viewpoint is this:

Zero is a number. But the division operator is restricted so that division by zero is undefined.

In other words, instead of restricting the number, they just restrict the operator.

They could have thrown out zero if they had wanted. But they considered it a more elegant solution to just restrict the division operator.

I have a collection with x, y and class values in R
Is there an easy way to calculate means per class and the covariance matrix without splitting it in one collection per class?

Has anyone dealt with having to learn while exhausted? I've got narcolepsy and constantly feel like I'm dead even after I wake up from any amount of sleep. I feel like material just isn't being absorbed and internalized, my focus simply doesn't exist, and when I run into something I truly don't understand yet I end up feeling like I've got a fucking tumor in the front of my brain. If there's anything I can do to help even a little bit, I'd like to know.

red bull

I'm already on real stimulants, it doesn't really do anything except help me not fall asleep. I still feel exhausted and in a hellish silent-hill thick fog.

Is there some formula to find the exact angle if I have both x and y positions on the unit circle?

I know that if I take acos(x) or a asin(y) I will get an angle. But there will be two solutions. I need to find which one of the two is the correct one.

Doing some AI programming and need it to make the AI shoot in the correct direction

>I know that if I take acos(x) or a asin(y) I will get an angle. But there will be two solutions. I need to find which one of the two is the correct one.
Do both, compare the four solutions and use the two that are the same

Should I copy the teachers QED sign?
[eqn]\not \triangle[/eqn]

Orgo II focuses primarily on more in depth analysis of functional groups and their reactions, I can't really say it's necessarily harder since it covers stuff you've learned about already but in more depth

You might be able to use some identities to get things in terms of Tan, then you can use atan2 to fix the quadrant problems

I know nothing about set theory. Is solving problems like
S + {2, 7} = {x, y, z}, Solve for S(I realize this might be unsolvable, it's just an example)
Part of set theory? If so, what are the applications of problems like these?

define '+' for sets first

Yeah I ended up doing it like this. Was hoping for some more effecient solution but it'll do!

Hmm. Interesting. I'm not very good at Tan stuff. I'll try to look it up. Thanks!

As a guy who is weak at maths (lazy) how do I get better? I'm starting science undergrad next year so I want to be prepared? What are the best guides/textbooks? I'll be studying linear algebra and calculus in 1st semester so they're top priority

sorry i put the ? on second sentence by mistake

Besides
No, if I understood you correctly. Set theory is a lot about our axioms (ZFC) and logic. Nowadays (what I have seen so far, naming a few buzzwords) about non-materialistic set theories, large cardinals, advanced combinatorics and set-theoretic-concepts like forcing, ultrafilters etc.