Why is pi here? And why is it squared? A geometric answer to the Basel problem

Why is pi here? And why is it squared? A geometric answer to the Basel problem
3Blue1Brown

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A most beautiful proof of the Basel problem, using light.
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Special thanks to these supporters: http://3b1b.co/basel-thanks
This video was sponsored by Brilliant: https://brilliant.org/3b1b

Brilliant's principles list that I referenced:
https://brilliant.org/principles/

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The content here was based on a paper by Johan Wästlund
http://www.math.chalmers.se/~wastlund...

Check out Mathologer's video on the many cousins of the Pythagorean theorem:
https://youtu.be/p-0SOWbzUYI

On the topic of Mathologer, he also has a nice video about the Basel problem:
https://youtu.be/yPl64xi_ZZA

A simple Geogebra to play around with the Inverse Pythagorean Theorem argument shown here.
https://ggbm.at/yPExUf7b

Some of you may be concerned about the final step here where we said the circle approaches a line.  What about all the lighthouses on the far end?  Well, a more careful calculation will show that the contributions from those lights become more negligible.  In fact, the contributions from almost all lights become negligible.  For the ambitious among you, see this paper for full details.

If you want to contribute translated subtitles or to help review those that have already been made by others and need approval, you can click the gear icon in the video and go to subtitles/cc, then "add subtitles/cc".  I really appreciate those who do this, as it helps make the lessons accessible to more people.

https://youtu.be/d-o3eB9sfls

https://heisme.skymoon.info/article/SuggInfo/1349  

가을이 와서 열매를 맺을 때가 되면 봄날의 꽃이 얼마나 예뻤는지 얼마나 오래 피어 있었는지는 중요하지 않았음을 알게 된단다. 꽃은 그저 벌과 나비를 불러 들이기 위해 피었을 뿐이었지 [하늘-봄날의 꽃을 기억하며]