Overrated theorems

Nope. They're both there.

It's not "defined" as a sine wave. It's emergent. It shows up when you expand sin(ix) as a Taylor series.

Fuck, you're right, I'm a brainless and sorry for writing this.
Thought there was an i missing in the exponent at first.

Sorry, I was confused. It is the opposite, it appears in the series of e^(ix).