One derivation of Euler's equation using series expansions for e^x, cos(f), sin(f).

Reference http://www.ee.nmt.edu/~elosery/lectures/Quadrature_signals.pdf

[complex numbers, Euler, Euler's identity, Euler's equation]

Reference http://www.ee.nmt.edu/~elosery/lectures/Quadrature_signals.pdf

[complex numbers, Euler, Euler's identity, Euler's equation]