Where can I get more math explanations like this video?

Try this channel:
https://www.youtube.com/user/numberphile

Ian’s doing similar stuff on the 4th grade program on Khan Academy. (The easy half, not the hard half. My brain did backflips during that part.)

@Seek
https://www.youtube.com/watch?v=ynfu6hSqViI

Legit, bro.

The first problem could be solved more easily than was shown. If you remove the two circles from the rectangle then the red region below the diagonal is the same as the remaining area above the diagonal, so the red area is just half of rectangle minus two circles.

Do the Chinese learn trigonometry in sixth grade? The speaker should have mentioned that you need a calculator to solve the second problem, since that is the only way of calculating arc tan ½. Given enough time, I think I might have been able to solve the second problem. It sure did require a lot of work.

You might like videos by Arthur Benjamin. Do a google search and you will see a bunch.

For the second half, I’d demand the teacher demonstrate for me any reason anyone would possibly need to do that math, and why that amount of math-ing is worth the hassle.