Latex 跨行大括号的使用

方法一

\begin{eqnarray}
		\hat{u}_{i,t} = \left\{
		\begin{aligned}
			&\frac{C_{i,t}}{T_{i,t}} = 
\frac{\sum^{T_{i,t}}_{k=1}\kappa_{i,k}}{T_{i,t}}\quad &T_{i,t} > 0\\
			&u_{default} &T_{i,t} = 0,
		\end{aligned}
		\right.
	\end{eqnarray}

&用来设置对齐

效果

方法二

$$
T_{i,t+1}=\left\{
		\begin{array}{lcl}
			t  &     & if\ v_i\ \in \cup_m \tau_{m,t},\\
	     T_{i,t}  &     & otherwise\\
		\end{array} \right.
$$

效果

去掉{eqnarray}则不会显示编号，注意\right后面的.