3 ms·

I started reading this, and the article is very approachable, but it’s flawed from almost the very beginning. He uses the angle addition formulas to derive the

by dmayle 2y ago

I started reading this, and the article is very approachable, but it’s flawed from almost the very beginning. He uses the angle addition formulas to derive the Pythagorean theorem, but this derivation only works because he predefined sine and cosine as odd and even functions, which hasn’t been proven

lupire 2y ago
He did gloss over it, but odd cos and even sin is obvious as soon as you define signed angles (which and lengths (which he forgot to mention). Sin(t) clearly has the same sign as t. (That's why it's called "sin" ;-) )