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

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

Block:

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

Escaped square brackets:

$$\sin A \cos B = \frac{1}{2}\left[ \sin(A-B)+\sin(A+B) \right]$$

Environment:

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

In equation $\eqref{eq:sample}$, we find the value of an interesting integral:

$$\begin{equation} \int_0^\infty \frac{x^3}{e^x-1}\,dx = \frac{\pi^4}{15} \label{eq:sample} \end{equation}$$