int Cos(x) -

$\int Cos(x) = Sin(x)$

$\int \frac{e^{ix} + e^{-ix}}{2} = Cos(x)$

$\int \frac{e^{ix}}{2} + \int \frac{e^{-ix}}{2}$

$\frac{e^{ix}}{2i} – \frac{e^{-ix}}{2i}$

$\frac{e^{ix} – e^{-ix}}{2*i} = Sin(x)$

Optimized by Optimole