$a^2 + b^2 = c^2$

$1+2+\dots+n=\frac{n(n+1)}{2}$

$$\frac{d}{dx}\left( \int_{0}^{x} f(u)\,du\right)=f(x)$$

$$\begin{align*} e^x & = 1 + x + \frac{x^2}{2} + \frac{x^3}{6} + \cdots \\ & = \sum_{n\geq 0} \frac{x^n}{n!} \end{align*}$$