测试 LaTeX

This is an array.

\begin{array}{cc} a & b \\ c & d \end{array}

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}