对齐平等 = 一个在另一个之下

Question

我有以下 LaTeX 格式的数学文本源，我想将所有等式 (=) 对齐，使它们一个在另一个的正下方。我该怎么做？请参阅此问题的最后两行。有人可以将这个等式链重写到 ALIGN 环境中吗？我被它难住了。

\documentclass{article}


\usepackage{newtxtext}
\usepackage{newtxmath}
\usepackage{amsmath}


\begin{document}

It is clearer if you define $q_i = p_i \cdot f_i \cdot \overline{f}_i$

This is how it should be.

Then

$p \cdot f = p \cdot b_i \cdot f_i \qquad \text{(since } f = b_i \cdot f_i)$

$= d^*_i \cdot p_i \cdot f_i \qquad\text{(by naturality)}$

$= d^*_i \cdot p_i \cdot f_i \cdot \overline{f}_i \cdot f_i$ = \qquad (as $\overline{f}_i \cdot f_i = 1$)

$= d^*_i \cdot q_i \cdot f_i  \qquad \text{(by the definition of} q_i)$

$= q \cdot b_i \cdot f_i  \qquad \text{(by naturality)}$

$= q \cdot f  \text{(by naturality)}$

Hope that helps.

\end{document}

Answer 1

更新

文本左对齐

\documentclass[]{article}
\usepackage{amsmath}

\begin{document}

\begin{align}
 &\text{It is clearer if you define} &q_i &= p_i \cdot f_i \cdot \overline{f}_i\\
&\text{This is how it should be} & p \cdot f &= p \cdot b_i \cdot f_i\\
&\text{then} &&= d^*_i \cdot p_i \cdot f_i \qquad \text{(by neutrality)}
\end{align}
\end{document}

文本右对齐

\documentclass[]{article}
\usepackage{amsmath}

\begin{document}

\begin{align}
 \text{It is clearer if you define}& &q_i &= p_i \cdot f_i \cdot \overline{f}_i\\
\text{This is how it should be}& & p \cdot f &= p \cdot b_i \cdot f_i\\
\text{then} &&&= d^*_i \cdot p_i \cdot f_i \qquad \text{(by neutrality)}
\end{align}
\end{document}