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.
Help fund future projects: https://www.patreon.com/3blue1brown
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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  

남해의 어느 섬에는 일년 내내 가을의 향기가 남아 있는 오솔길이 있다. 그 곳은 한낮에도 온통 우거진 숲 사이로 작은 빛줄기들만 새어 들어올 뿐 조용한 가을의 향기가 일년 내내 남아 있는 곳이다 [하늘-8년만에 갔던 그 곳 (지심도)]
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쇼쇼쇼 548회 (1975) :영상

[영상] 하늘 0 11,232
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Musica decada 1950-1960 :영상

[영상] 하늘 0 10,108