帮助对齐

Question

有人能用这个命令把它写出来吗alignat？它应该在暗示符号和等号处对齐，所有项都向等号对齐。

Answer 1

\documentclass[12pt]{article}
\usepackage{amsmath}
\begin{document}
\begin{alignat*}{2}
&&\dfrac{a}{b} &= 0.5\\
\implies&&a &= 0.5b\\
\implies&&ka &=0.5kb\\
\implies&\quad&k^2a^2 &= 0.25k^2 b^2
\end{alignat*}
\end{document}

也可以使用 TABstack 或aligned块轻松完成。

\documentclass[12pt]{article}
\usepackage{tabstackengine,amsmath}
\TABstackMath
\setstackgap{S}{8pt}
\begin{document}
\[
\alignShortstack{
&&\dfrac{a}{b} =& 0.5\\
\implies&&a =& 0.5b\\
\implies&&ka =&0.5kb\\
\implies&&k^2a^2 =& 0.25k^2 b^2
}
\]

\[
\begin{aligned}
&&\dfrac{a}{b} &= 0.5\\
\implies&&a &= 0.5b\\
\implies&&ka &=0.5kb\\
\implies&&k^2a^2 &= 0.25k^2 b^2
\end{aligned}
\]

\end{document}

Answer 2

使用 aligned 和 alignat：

\documentclass[12pt]{article}
\usepackage{amsmath}

\begin{document}
\[
\begin{aligned}
            &   &   \frac{a}{b} & = 0.5         \\
\implies    &   &   a           & = 0.5b        \\
\implies    &   &   ka          & = 0.5kb       \\
\implies    &   &   k^2a^2      &  =0.25k^2 b^2
\end{aligned}
\]

or

\[
\begin{aligned}
            &\quad  &   \frac{a}{b} & = 0.5         \\
\implies    &       &   a           & = 0.5b        \\
\implies    &       &   ka          & = 0.5kb       \\
\implies    &       &   k^2a^2      &  =0.25k^2 b^2
\end{aligned}
\]

or

\begin{alignat*}{3}
            &\quad  &  \frac{a}{b} & = 0.5         \\
\implies    &       &   a          & = 0.5b        \\
\implies    &       &   ka         & = 0.5kb       \\
\implies    &       &   k^2a^2     & = 0.25k^2 b^2
\end{alignat*}

\end{document}