solution verification - Doubt on a fake proof of $e^{i\pi}=-1$. - Mathematics Stack Exchange
Euler's Formula for Complex Numbers
functional analysis - Show that the exponentials $1, e^{2\pi ix}, \dots , e ^{2\pi ikx}, \dots$ form the basis for trigonometric polynomials. - Mathematics Stack Exchange
Why does [math]e^{iπ/2} = i[/math]? - Quora
If `x_r = cos (pi/2^r) + i sin(pi/2^r) , z_t = cos(pi/3^t)+i sin (pi/3^t)` where `r= 1, 2 - YouTube