我想将下面的等式分成两部分。这似乎是非常基本的事情。
\begin{equation}
\zeta_k(x) = \frac{\sin (\frac{1}{2} (x - x_0)) \cdots \sin(\frac{1}{2} (x-x_{k-1}))}
{ \sin ( \frac{1}{2} (x_k - x_0)) \cdots \sin(\frac{1}{2} (x_k - x_{k-1}))} %
%
\frac{\sin ( \frac{1}{2} (x - x_{k+1})) \cdots %
\sin(\frac{1}{2} (x - x_{2n}))}{\sin(\frac{1}{2} (x_k - x_{k+1})) \cdots %
\sin(\frac{1}{2} (x_k - x_{2n}))}
\label{eq3}
\end{equation}
我插入了 amsmath 包并尝试使用 begin split 等，但无法将方程分成两行，其中一行包含
\zeta_k(x) = \frac{\sin (\frac{1}{2} (x - x_0)) \cdots \sin(\frac{1}{2} (x-x_{k-1}))}
{ \sin ( \frac{1}{2} (x_k - x_0)) \cdots \sin(\frac{1}{2} (x_k - x_{k-1}))} %
%
另一个包含
\frac{\sin ( \frac{1}{2} (x - x_{k+1})) \cdots %
\sin(\frac{1}{2} (x - x_{2n}))}{\sin(\frac{1}{2} (x_k - x_{k+1})) \cdots %
\sin(\frac{1}{2} (x_k - x_{2n}))}
有什么建议么？
答案1
我会用（回忆录不相关）
\documentclass[a4paper]{memoir}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{split}
\zeta_k(x) ={} & \frac{\sin (\frac{1}{2} (x - x_0)) \cdots
\sin(\frac{1}{2} (x-x_{k-1}))} { \sin ( \frac{1}{2} (x_k - x_0))
\cdots \sin(\frac{1}{2} (x_k - x_{k-1}))} %
%
\\
& \times \frac{\sin ( \frac{1}{2} (x - x_{k+1})) \cdots %
\sin(\frac{1}{2} (x - x_{2n}))}{\sin(\frac{1}{2} (x_k -
x_{k+1})) \cdots %
\sin(\frac{1}{2} (x_k - x_{2n}))}
\end{split}
\label{eq3}
\end{equation}
\end{document}