# Equation number not on the extreme right?

I am trying to number the equation in my thesis. All of the equation numbers are being displayed correctly on the extreme right (of the text area). However, in one equation, I am facing a little problem. The equation number in this case is stick to the equation and is looking quite annoying in my thesis. The code of the equation is as follows

\documentclass{article}
\begin{document}
$${\mu ^'}\left( {{x_{mn}}} \right) = \left\{ \begin{array}{l} 2{\left( {{\mu _{mn}}} \right)^2},0 \le {\mu _{mn}} < 0.5 \\ 1 - 2{\left( {1 - {\mu _{mn}}} \right)^2},0.5 \le {\mu _{mn}} \le 1 \\ \end{array} \right.$$
\end{document}


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Welcome to TeX.sx! –  hpesoj626 Mar 14 '13 at 12:19
I made a rollback since with the edit, there was no problem anymore. Please don't fix such errors in the code in questions! (And please don't approve such edits.) Or shall we discuss this on Meta? –  Hendrik Vogt Mar 14 '13 at 12:30
@HendrikVogt I agree, questions shouldn’t be answered by editing them. Though, in this case I approved since the wrong syntax made the MWE not even compilable. I wonder how one got an—albeit faulty–output? –  Qrrbrbirlbel Mar 14 '13 at 12:35
@Qrrbrbirlbel: Hit enter often enough, or even better, hit q and enter! –  Hendrik Vogt Mar 14 '13 at 12:52
Ok. I shouldn't have corrected the \mu^' in the original post. Apologies. –  Jubobs Mar 14 '13 at 12:52

As pointed out in the comments, use \mu', not \mu^', or you will get an error. Once this modification has been made, the equation number appears as far to the right as possible, given the current geometry:

\documentclass{article}

\usepackage[showframe]{geometry}

\begin{document}
$${\mu'}\left( {{x_{mn}}} \right) = \left\{ \begin{array}{l} 2{\left( {{\mu _{mn}}} \right)^2},0 \le {\mu _{mn}} < 0.5 \\ 1 - 2{\left( {1 - {\mu _{mn}}} \right)^2},0.5 \le {\mu _{mn}} \le 1 \\ \end{array} \right.$$
\end{document}

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Note it's more common (and equivalent) to use \mu' rather than \mu^\prime –  David Carlisle Mar 14 '13 at 12:46
@DavidCarlisle Ok. I'll modify my solution accordingly. –  Jubobs Mar 14 '13 at 12:49

Make sure your code actually compile without errors: {\mu ^'} -> \mu', then I have no problems. In math mode, ' is equivalent to ^{\prime}.

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