Greg Back

Sine-Cosine-Exponential Identities

Useful in my Digital Signal Processing class...

$\cos x = \mathrm{Re}\{e^{ix}\} ={e^{ix} + e^{-ix} \over 2}$
$\sin x = \mathrm{Im}\{e^{ix}\} ={e^{ix} - e^{-ix} \over 2i}.$
$e^{ix} = \cos x + i \sin x \;$
$\mathrm{sinc}(x) = \frac{\sin(\pi x)}{\pi x}.\,\!$

Source: Wikipedia - Euler's formula

Source: Wikipedia - Sinc function