/sci/ - Science & Math

>>10681909
Have you tried logarithms?

>>10681909
Now that one is up:
Is a conditional statement defining causation between two statements?

This is /sqb/

>>10681993
> Is a conditional statement defining causation between two statements?
No. Logic doesn't have "causation". If you have ¬A∨B, that means that A is false or B is true. You can't say that A being false "causes" B to be true or B being true "causes" A to be false. Note that both AB and ¬B¬A are exactly equivalent to ¬A∨B (and to each other); none of the three forms imply causation.

>>10681909
Does anyone know how the answer was found here? It should be a basic moments equations using fr though I have no idea how they've gotten 66.7 for the answer. Here's the question;

"A spanner 15cm long is used to undo a nut against a maximum frictional torque of 10Nm. What is the minimum force that must be applied to the spanner to undo the nut?"

>>10681909
For anyone that has strong autism, this thread is now /sqt/. I have very strong autism and I went and checked the catalog after I read >>10681993.

>>10682048
>No.
No him. I get that there is no thing as causality in logic, but still I have this idea that it is widely agreed upon that implication is a formalization of the idea of causality in the context of logic. Is this wrong?

>>10682048
Thanks senpai, helped me out

>>10682048
So conditional statement is just a different way of saying implication (as it is used in maths)?

>>10681909
I often laugh at my own jokes. Does that mean that I'm schizophrenic?

>>10682212
No

>>10682217
But laughter are spawned through surprise, if you know what's coming, how can it be funny?

>>10682212
>Posts on /sci/
Yep.

>>10682228
>But laughter are spawned through surprise
Says who?

>>10682054
Why would you ever want to undo a nut, reverse orgasms sound horribly unsatisfying.

what would be a good reason and what would not be a good reason to go into a masters program?

from last tred nobody replied:
a Convex closed curve is inscribed in another convex closed curve, prove that the former curve has always smaller perimeter than the latter one.

>>10682262
self-important scientists who want to objectivize everything

>>10682262
empirically derived data

Tags: ACOUSTIC IMPEDANCE, SOUND REFLECTION

If a sound wave meets the interface of two materials with wildly differing specific acoustic impedance, will equal amounts of sound be reflected regardless of if it's moving from medium 1 to medium 2, or from medium 2 to medium 1?
For example a sound wave in air encountering a concrete wall, and vice versa. I'm assuming this is why you use impedence matching to reduce the difference and hence reduce reflection.

>>10682103
It is. For example, a false statement implies literally anything else.

>>10681909
Hey, im a venezuelan EE student.
I applied for some summer internship positions in america, I would need sponsorship for a work visa during the summer if I were to be hired for an internship.
What are my chances of getting accepted?

>>10682048
> Note that both AB and ¬B¬A
The arrow got eaten; it should have been roughly:
> Note that both A->B and ¬B->¬A

>>10682573
Google "Archimedes axiom proof convex curve" or "Crofton formula" and check which makes more sense for you

>>10682054
[math]M = F \cdot r \implies F = M/r \\ F = 10 / 0.15 = 66.7[/math]


wtf anon that's brainlet territory

>>10682977
I figured it out just before work, god I'm so angry at myself! Thanks a tonne anyhow.

>>10681909
Dual degree in business+computer science? Any experience with this? Is it a good idea? How can I optimize this experience to cut the fat?

>>10682727
Didn't know you guys still had electricity, as well as internet access. Cool. Good luck man!

>>10683819
please stop coming here

Anyone here knows the formula for an inclined cylinder in 3d space that follows a given diretrix ?

I am writing a report where I compare the performance of an ARM processor and and x86-64 processor.
I want to take price and power consumption into the calculation of performance.
Performance is measured with a benchmark and also to see how many seconds on average it takes to run a certain set of programs.
I know that to find the performance-cost/power ratio for the benchmark is to divide its result by cost/power, as the higher the cost/power the more it drags down the ratio.
But what about measuring in seconds? As the less seconds it takes, the better the performance. But dividing an already fast processor by a large number would produce an even smaller number and wouldn't provide any sort of proper ratio right?

>>10685508
The power-price and benchmark-price curves don''t go through the origin. (e.g., if you have a 1 Gflops processor that benchmarks at 904 whatevers for 100 bux, that doesn't mean you can necessarily buy a 250 Mflops processor that benchmarks at 226 whatevers for 25 bux.)
I suggest you get data for existing processors and plot their power or benchmarks against their price. Build a regression (lmaomsexcel does it easily) and compare by how much the tested processors overperform or underperform compared to what's expected of their price.

Can you please explain index shift in summation to a brainlet like me?

I want to solve things like pic related but I don't know what to do

Why is sqrt(20)/2 equal to sqrt(5), and not sqrt(10)?

>>10686219
(20)^(1/2) * 1/2 = (20)^(1/2) * 1/(4)^(1/2) = (20/4)^(1/2)

>>10686112
The LHS is just (n-1)*n^3, the RHS is an arithmetic series which has a closed form, (m-n+1)(7n+7m+2)/2. Equating the two terms gives a quadratic in m which can be solved via the quadratic formula. Whether or not it has any integer solutions is a different matter.

Can someone help me solve this problem? It's basic vector stuff but I don't know how to approach it.

>>10686564
(same anon) Also, I've been assuming that O is some random point. Is O the origin?

how the fuck does two-dimensional time work
what the fuck?

What's science been up to the past year?

Did we invent any cool new materials or cure diseases or anything?

>>10686569
> Is O the origin?
Yes. OA is just A.
OA-OB+OC=(3,α,0) => ||OA-OB+OC||=√(α^2+9) => α=√7
OB=(0,1,β) => ||OB||=√(β^2+1) => β=√15

>>10686760
Thanks. I'm kind of retarded for trying to solve it assuming O was some random point. Solved using the origin and got the answer in like 2 seconds.

>>10681909
Anyone know any good textbooks on invertebrate biology, evolution of marine mammals or early geologic age sea life?

>>10685547
no, that's not what I meant. I am supposed to compare their performance/cost to see which one has superior performance-cost/power ratio. Of course this is a real case
https://www.cpubenchmark.net/cpu_value_available.html

>>10682212
It's pretty normal among socialites. Whenever you hear roaring laughter from a group, a lot of times it's just the person who told the story, with maybe 2-3 nervous chuckles that maintain the illusion.

>>10686644
Cystic Fibrosis treatments are vastly improved to a point where soon, patients might have near normal lung behavior. Hep C was cured a few years ago. Pain killers that inhibit nerve activity and don't cause addiction are on the way.

>>10686769
evolution isnt real
hail (((jesus)))

why do we use water in nuclear reactors? does it have any properties that make it especially good for steamin up and rotating fans? can you think of a better liquid to use? why?

I've got a question /sci/
How do you stop being stupid? I've recently finished the book "Book of Proofs" which is recommended to me because it's simple and easy to grasp. Indeed most of the theorems are simple and easy to understand but I always get stuck on the more diffucult exercises that makes use of said theorems. I usually resort to checking the answers for those questions.
I don't want to be dumb.

Given a standard 52-card deck, how many 4-card hands are there for which all 4 cards are of different suits, or all 4 cards are red. Why isn't this just 13^4/4! + (26 choose 4)? The error, I suspect, is in the 13^4/4! part, but here I'm just choosing a single card of each suit, and then dividing by the number of permutations of a hand of 4 cards.

>>10687212
The trick to not being dumb is to chose an area of expertise noone else is in, so that you have no competition. It's like speed-running in the gaming sphere.

>>10681909
How would I go about proving or disproving the following? Never took a formal class on Group theory, just self taught and I happened to notice this holds for n=2,3 so far.

The group G generated by < x, y | x^2 = y^2 = (xy)^n = e > for n > 1 (e is the identity element) is isomorphic to the group of permutations on n objects, S(n).

I don‘t have any formal maths beyond calc so pls be autism friendly

>>10687205
Because it’s plentiful and basically free

What's the evolutionary purpose of hymen

>>10687424
Warranty is void if seal is broken

>>10687433
it's hardly an advantage for women

>>10686644
A lot of scientific breakthroughs are internally relevant, accelerating the progress of science without themselves producing results relevant to the general public. The most groundbreaking paper I heard of recently was linking Cas to graphene which lets us convert the presence of particular DNA sequences in solution to an electrical signal, which basically BTFOs the last 40 years of biotech methods.

>>10687440
Depends on how it's used

>>10687395
For 4 different suits, the number of ways is
(13*4)*(13*3)*(13*2)*(13*1)/4! = 13^4*(4*3*2*1)/4! = 13^4 = 28561.
IOW, you get to pick one card from each suit, or get to pick one card from 4,3,2,1 complete suits then cancel out the 4! different orders.

For four red cards, it's just 26C4 = 14950.

>>10687400
Well I kinda want to be an mathematician. how do I excel in math then? I lack the ability to "think out of the box".

Okay asking again but in a more intuitive way:

Say you have 2 contractors who offer to build a bridge. One contractor offers to finish the bridge in 1 year but it will cost $100 million
The other contractor offers to build it in 4 years, but the price would only be $20 million. We assume the quality is the exact same.

How would you find out which one has the more cost-effective deal? As in who has the most reasonable cost for the time it takes to construct. And how would you derive a formula for this?

Why are doctors so stupid?

>>10687688
Depends on how much you value each year, and exactly what you mean by "cost-effective".

>>10687688
Five million a year vs 100 million a year. Don't make sense huh?

Where does wind actually come from?

>>10687703
Fuck you guys. Probably just as stupid. You think an education makes you smart. I'm twice as smart with 1/16 the education. In conclusion: Fuck you.

Baryons have an odd ([math]\geq[/math]3) amount of quarks, mesons have an even ([math]\geq[/math]2) amount.

Why would this statement be false?

>>10687088
>Pain killers that inhibit nerve activity
Is that a good idea? Silently and unheard doing more damage to the problematic body part?

>>10687205
Probably Nuclear Weapon production.

Throium (salt) reactors would just consume all fuel.

>>10687688
Externalities?

If I drop my bottle of water, is it theoretically possible that it falls through the floor by quantum tunneling or something?

>>10688342
I wouldn't want to spoil the question by tagging but none of these ass holes will answer you anyhow. I have a wooden dresser full of gunpowder and associated shit and a sealed bottle of ammonia on top of it. When I picked up the bottle, the wood was burned black under it, charred to a crisp. Moved the bottle and it is still full years later. No leaks.

Time value of money. So first we’d have to determine whether the cash inflow from the bridge being completed is worth the 100 million outflow given a certain discount rate, usually the rate of GDP growth for stuff like this. Then it’s simply arithmetic. NPV positive, pick the 1 year contractor. NPV negative, either renegotiate price or choose contractor 2.

>>10688398
>>10687688
Meant to reply to this

>>10687413
Let z = xy, then you can write every element of G uniquely in the form y * z^k or just z^k for some k between 0 and n - 1 (prove this). For example, x = y * z^(-1) = y * z^(n - 1). So the order of G is 2n (in fact, G is actually the dihedral group because yzy = z^-1), whereas the order of Sn is n!

In conclusion, G is isomorphic to Sn only when n = 3

>>10687721
>>10687741
>>10688166
>>10688398

Oh my fucking goodness, just answer the fucking question and understand that the post was just a overly simplified example of my problem, you drooling troglodytes. The question was not regarding any real world scenario of contracting. It's just that none of you can really comprehend this question here >>10685508 so I had to make it more simple for you to fucking understand
I came here for a stupid question, yes? I also came here to expect at least some proper answers instead of a bunch of assburgers giving me (You)s thinking they are "le ebic XD"

Of course, the second contractor is more cost effective, but I'm not sure how you can prove that and derive a product that can be used for reference.
Would you do
[math]frac{years}{cost}[/math}
?
That doesn't seem right and can't really tell everything

>>10688516
What a fucking idiot.

>>10688678
yup

Assuming the decimal series of irrational numbers and physical constants are unique: Would it be possible to fingerprint their decimal series and compare them to a high precision, physical measurement, and determine what components were in say a 10 decimal measurement?
Like, a vibration in the instrument would give pi, and a 40% match with the vaccuum permeability would indicate whatever that indicates. Could decimal fingerprinting work? Has anyone tried it?

>>10688516
The bar is usually low in /sqt/, but wow. You're retarded.

>>10687424
It's probably a compromise between having a hole to push a baby through and not having a hole for bacteria and stuff to get in and infect you while you're young and immunologically vulnerable.

>>10687899
Sun heats the air, hot air moves up, cold air moves down, other air fills the gaps.

How do you guys get better at memorizing things?
I mean this in general.
I can always study and use anki cards to remember vocab but what about memorizing long stories, and for long times?

>>10689408
I think you need to get a firm grasp on your attentiveness. For example, Pick a (moderately complex) thing you can remember well, without having studied it much. What makes that piece of information different from what you can't pick up easily right now?

>>10688516
It's not my problem if you don't grasp "Externalities".

We'd have:
y = 100 + k * min(t,1)
and
y = 20 + k * min(t,4)

y ... Total cost (including cost of necessary transportation)
t ... Number of years passed
k ... Additional cost per year passed

Let's say our essential transports incur a cost of 123 million per year.

https://www.wolframalpha.com/input/?i=plot+100+%2B+123+*+min(t,1),+20+%2B+123+*+min(t,4),+t%3D0+to+5