Live data from Hacker News

Why does e to pi i equal -1? (2015) [video]

youtube.com

11–20 of 148 posts

Re: Why does e to pi i equal -1? (2015) [video]

#15

Is it pure chance that this was posted only two or three days after I watched it along with a few other e to pi = -1 videos? Randomness aside. 3blue1brown makes some wonderful math videos that I find really explain the intuitiveness of some of the ideas. I was unfortunately cursed with a math teacher who for whatever reason required us to memorize until we passed the test. Imaginary numbers were taught as "something…

Richard Feynman used to go up to people all the time and he'd say "You won't believe what happened to me today... you won't believe what happened to me" and people would say "What?" and he'd say "Absolutely nothing".

I agree wholeheartedly with the quality assessment of 3blue1brown videos. All mathematics should be clear and intuitive, by definition :)

Re: Why does e to pi i equal -1? (2015) [video]

#16
e^x = an infinite series

if you substitute x = iz

you can split the even and odd terms of the infinite series into cos and sin

e^iz = cos z + i sin z

evaluating at z = pi yields

cos pi + i sin pi

-1 + 0i = -1

the exponential function maps the imaginary axis to the unit circle. pi gets mapped to -1.

This shows its true, but the "why" and real understanding requires calculus and the first week of complex analysis. Otherwise you are just parroting a set of facts.

Post reply on HN