对齐公式问题

Question

\documentclass{article}

\usepackage{amsmath}

\begin{document}

\begin{align*}
y ={}& \frac{1}{n!} \left\lbrace \int + f(a) \right. \\
     &\left. \vphantom{\int} + [h(u)+\phi(x)] + C \right\rbrace 
\end{align*}
\end{document}

如何将加号与分数对齐？谢谢。

Answer 1

对齐其实并不必要，而且multline可能有用。如果您认为对齐很重要，这里有三个建议。

\documentclass{article}

\usepackage{amsmath}

\begin{document}

The following aligns the + with the fraction
\begin{equation*}
\begin{split}
y ={} & \frac{1}{n!} \biggl\lbrace \int + f(a) \\
      & {} + [h(u)+\phi(x)] + C \biggr\rbrace
\end{split}
\end{equation*}
but with a slight offset; with the following the
offset is removed
\begin{equation*}
\begin{split}
y ={} & \frac{1}{n!} \biggl\lbrace \int + f(a) \\
      & {\mspace{-\medmuskip}} + [h(u)+\phi(x)] + C \biggr\rbrace
\end{split}
\end{equation*}
However, I'd align with the integral sign 
\begin{equation*}
\begin{split}
y = \frac{1}{n!} \biggl\lbrace &\!\int + f(a) \\
      & {\mspace{-\medmuskip}} + [h(u)+\phi(x)] + C \biggr\rbrace
\end{split}
\end{equation*}

\end{document}

Answer 2

尝试

\begin{align*}
y &= \frac{1}{n!} \left\lbrace \int + f(a) \right. \\
  &\phantom{=} \left. \vphantom{\int} + [h(u)+\phi(x)] + C \right\rbrace 
\end{align*}    

Answer 3

这里不需要对齐（这就是为什么需要\phantom等来隐藏对齐点），你只需要一条需要断开的线（所以我假设你的文本宽度很窄），例如：

\documentclass[twocolumn,a5paper]{article}

\usepackage{amsmath}

\begin{document}

\begin{multline*}
y =\frac{1}{n!} \Bigl\lbrace \int + f(a)  \\
    {} + [h(u)+\phi(x)] + C \Bigr\rbrace 
\end{multline*}
\end{document}