4

How can I center an equation according to \Leftrightarrow? I would like the second\Leftrightarrow to be below the first.

\documentclass[12pt,a4paper]{report}
\begin{document}

\begin{equation}
x = r \cos \varphi = 0 \qquad \Leftrightarrow \qquad \cos\varphi = 0,
\end{equation}

\begin{equation}
y= 56 \qquad \Leftrightarrow \qquad \sin\alpha = ,
\end{equation}


\end{document}
  • I can't help but comment that if \Leftrightarrow is supposed to mean "if and only if", the statement in the first equatioin is incorrect: r\cos\varphi=0 is true if either \cos\varphi=0 or r=0. – Mico Dec 26 '18 at 14:03
  • 2
    \Leftrightarrow can be replaced with \iff – user94293 Dec 26 '18 at 20:19
5

I suggest you

  • replace the two equation enviroments with a single align environment, and
  • insert & alignment points in front of the two \Leftrightarrow directives.

The align LaTeX environment is one of several tools the amsmath package provides for typesetting multi-line math constructs. It would be an excellent idea for you to familiarize yourself with the user guide of the amsmath package.

enter image description here

\documentclass[12pt,a4paper]{report}
\usepackage{amsmath} % for 'align' environment
\begin{document}
\begin{align}
x=r\cos\varphi=0 \qquad &\Leftrightarrow \qquad \cos\varphi=0 \\
y = 56           \qquad &\Leftrightarrow \qquad \sin\alpha=\dotsc
\end{align}
\end{document}
3

Thank's to @Mico

\documentclass[12pt,a4paper]{report} 
\usepackage{amsmath}
\begin{document} 
\begin{align} 
    x = r \cos \varphi = 0 \qquad &\Leftrightarrow \qquad \cos\varphi = 0, \\
    y= 56 \qquad &\Leftrightarrow \qquad \sin\alpha =0 , 
\end{align} 
\end{document}

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