答案1
类似下面这样?(观察\mid
给出的间距比给出的间距更好|
。)
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
P(z_{n+1}=t \mid z_{1},\dots ,z_{n}; \alpha) =
\begin{cases}
\frac{n_t}{n+\alpha} & \text{if table $t$ is occupied}\\
\frac{\alpha}{n+\alpha} & \text{if table $t$ is empty}
\end{cases}
\end{equation}
\end{document}