split、multline、align、breqn 將方程式分成多行有什麼不同？

Question

抱歉，如果這個問題聽起來有點業餘，但我還沒有找到關於這四種環境之間的差異的很好的總結，用於多重方程式。它們的差異在哪裡，不同情況下應該選擇哪一種？

Answer 1

正如評論中所指出的，amsmath文件breqn中有幾個很好的例子，該mathtools包還具有幾個對齊的擴展版本amsmath。但這裡通常的風格是內聯回答而不是參考手冊，所以這是一個給出您提到的環境的基本用法的文檔。

\documentclass{article}

\usepackage{amsmath}
\usepackage{breqn}

\begin{document}

Align, from amsmath package:
numbered equations aligned at points marked
with \verb|&| usually just before a relation.
\begin{align}
a_1& =b_1+c_1\\
a_2& =b_2+c_2-d_2+e_2
\end{align}

split, also from amsmath,
similar alignment to align, but the whole construct fits within
equation (or other display math) and is numbered as a unit.
\begin{equation}\label{xx}
\begin{split}
a& =b+c-d\\
 & \quad +e-f\\
 & =g+h\\
 & =i
\end{split}
\end{equation}

multline, from amsmath
for lonq expressions taking more than one line,
with no specifed alignment points.
\begin{multline}
a+b+c+d+e+f+g+h+i+j+k+\\
l+m+n+o+p+q+r+s+t+w+x+y+z
\end{multline}


breqn is not part of the amsmath collection and is a highly experimental
package that tries to automate the line breaking.
Here it automatically spots the relations and adds
the line breaks and alignment points.
It also automatically handles the trailing full stop after the display.
\begin{dmath}
T(n) \hiderel{\leq} T(2^{\lceil\lg n\rceil})
  \leq c(3^{\lceil\lg n\rceil}
    -2^{\lceil\lg n\rceil})
  <3c\cdot3^{\lg n}
  =3c\,n^{\lg3}
\end{dmath}.

\end{document}