/sci/ - Science & Math

How do you guys revise math? I read that simply re-reading is not a good way to remember stuff, and that active recall is much better. The problem, is I don't know how to set up a good revision system.

I have no problem remembering computations, but I tend to forget (the less important) theorems, only the main things stick with me. Even the main theorems of a subject can become lost after 1-2 years of not using them.

I would like to set up a rather robust revision system. Flash cards don't work well for math, I don't think, at least.

How do you guys revise?

So there's the conic sections for quadratic equations of two variables. Of course there's also similar shapes by considering quadratic equations of three variables. Are these too "sections" of something? If so, what? Also, does this generalize to higher dimensions?

>>11761740
OP here. You're close. You just need to show now that no triples other than the ones you can construct like that exist.

Yes, don't relearn math from the ground up. Move on to new topics and stop being a coward wallowing in high school math. I understand the allure of "perfecting" your understanding before moving on, but evidence suggests (and I have personally experienced this, too) that only by moving on do you acquire a better understanding of preceding material.

>>11269527
It's not a perfect measurement, but it's a pretty good one. Find a better one, if you want. Actually the numbers I quoted were just CO2 emissions from fossil fuels, rather than total CO2 emissions. Here are more accurate statistics from 2017:

China: 7700 kg of CO2/capita
US: 15700 kg of CO2/capita
EU: 6944 kg of CO2/capita

China: $8827 per capita
US: $59532 per capita
EU: $34001 per capita

China: $1.15 per kg of CO2
US: $3.79 per kg of CO2
EU: $4.90 per kg of CO2

It would be interesting to see the results but for all GHG rather than just CO2, but I can only find European statistics for this.

Have you read a textbook that details solving problems like the one you posted, or are you just watching edutainment on youtube?

Also, chess is not inherently intellectual. It has the aura of it, and there's a certain prestige (at least among the common folk) of being good at it.

How is drinking coffee supposed to make you smart? I drink coffee because I like it, and it's a good pick-me-up.

Why are you reading random research papers? Even people who study a subject don't tend to sit around reading research papers until late in their education. You'd get much, much more out of reading textbooks. In fact, I very much doubt you even comprehend most of what you read in these papers.

Supposing I have a level set of some function that implicitly defines one of the variables as a function of the others, i.e. [math]G(x,y,z(x,y)) = K[/math]. Would it be correct for me say that [math]\frac{\partial G}{\partial x} = \frac{\partial G}{\partial z}\cdot \frac{\partial z}{\partial x}[/math]? "Cancelling" makes sense, but I'm having issues justifying it.

Considering the normal of a tangent plane to the graph of a function [math]f(x,y)[/math] is always
[math](\frac{\partial f}{\partial x},\frac{\partial f}{\partial y},-1)[/math](evaluated at whatever point we want to find the plane at) wouldn't that imply that the gradient of any surface in 3-space (level surface), or at least those that look like the graphs (i.e. only one z-coordinate per (x,y) coordinate), also be exactly that? Considering both the normal vector and the gradient vector are both orthogonal to the surface. I know it's not, but I don't know why. These two pieces of information seems very conflicting.

>>9113829
Wtf is category theory good for?

>>8654669
That pic is so uncomfortable desu

>bluray audio
>makeMKV to extract mkv files containing flac'd audio tracks for each album on the disc along with chapter metadata
>gMKVExtract to extract a usable cuesheet and turn the mkv into just the flac audio
>manually edit cuesheet
>use foobar2000 to turn single flac file into separate track flacs using the manually edited cuesheet
why the FUCK aren't there any FOSS bluray audio players that just fucking werk? why do I have to go through this fucking rigamarole of extracting and doing two passes of converting just to get something that's reasonably in-line with what i'd get with something any idiot could get from a regular cd?