色々な関数

\[ \begin{aligned} x \in \mathbb{C} \end{aligned} \]

\[ \begin{aligned} &\cos{x} = \frac{e^{ix} + e^{-ix}}{2} \\ &\sin{x} = \frac{e^{ix} - e^{-ix}}{2i} \end{aligned} \]