5

I would like the implies sign to be aligned for a group of equations, I am able to do this using the alignat environment

\begin{alignat*}{1}
   &\implies\quad x^2 + 2yx + 14y + y^2 = 5\\
   &\implies\quad r^2 + z^2 = 10\\
   &\implies\quad r=5\\
\end{alignat*}

However, this results in all the equations being left-justified. I would like them to be centred while the implied sign remains aligned. Somewhat similar to doing

\begin{gather*}
    \implies\quad x^2 + 2yx + 14y + y^2 = 5\\
    \implies\quad r^2 + z^2 = 10\\
    \implies\quad r=5\\
\end{gather*}

but with the implies sign as it was in the previously.

So, how do I align just 1 bit of a group of equations while everything else is centred?

4

As an alternative, here it is as a TABstack.

\documentclass{article}
\usepackage{amsmath}
\usepackage{tabstackengine}[2016-10-04]
\TABstackMath
\begin{document}
\[
\setstackgap{L}{1.3\baselineskip}
\tabularCenterstack{rc}{
   \implies& x^2 + 2yx + 14y + y^2 = 5\\
   \implies& r^2 + z^2 = 10\\
   \implies& r=5
}
\]
\end{document}

enter image description here

More conventionally, the array environment could be used

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
\renewcommand\arraystretch{1.3}
\begin{array}{rc}
   \implies& x^2 + 2yx + 14y + y^2 = 5\\
   \implies& r^2 + z^2 = 10\\
   \implies& r=5
\end{array}
\]
\end{document}
| improve this answer | |
3

You can use array with some tweaks for making it behave like an align* environment as far as vertical spacing and math style is concerned.

\documentclass{article}
\usepackage{amsmath}
\usepackage{array}

\newenvironment{impliesgathered}
 {\renewcommand{\arraystretch}{1.2}
  \begin{array}{r >{\displaystyle}c}}
 {\end{array}}

\begin{document}

Here is the desired alignment
\[
\begin{impliesgathered}
\Longrightarrow & x^2 + 2yx + 14y + y^2 = 5\\
\Longrightarrow & r^2 + z^2 = 10\\
\Longrightarrow & r=5
\end{impliesgathered}
\]
and here, for comparing the vertical spacing, the \texttt{align*}:
\begin{align*}
\Longrightarrow & x^2 + 2yx + 14y + y^2 = 5\\
\Longrightarrow & r^2 + z^2 = 10\\
\Longrightarrow & r=5
\end{align*}

\end{document}

enter image description here

| improve this answer | |

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