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I use the following codes with Winedt5.5 and Miktek2.8 :

\documentclass{amsart}[12pt]

\usepackage{amsmath, amsthm, amscd, amssymb, amsfonts}
\usepackage{environ}
\usepackage{mathtools}

\begin{document}

\begin{multline*}
|\frac{e}{e-1}(e^z-1)|\leq \frac{1}{2}e^{|z|}+ (1-\mu )e^{|z|}-1 +\frac{\mu\pi}{\pi^2 -1} \sinh(\pi|z|) +\frac{\mu}{\pi^2-1} (\cosh(\pi|z|)-1)
\\
\leq \frac{1}{2} e^{|z|} + (1-\mu )(e^{|z|}-1 )+\frac{\mu}{\pi-1}\sinh(\pi|z|)
 \\
\leq \frac{\pi-2}{2\pi}e^{|z|}+\frac{1}{\pi-1}(e^{\pi|z|}-1)
\\
 \leq  \left \frac{2}{\pi-1}(e^{\pi|z|}-1)
\end{multline*}

\end{document}

But I faced to the following errors:

Missing delimiter error <.inserted>.

< to be read again >

1.15 \end < multline* >

Can someone help me to improve the problem? Thanks.

3
  • 4
    The \left directive in the final row before \end{multline*} would look to be superfluous.
    – Mico
    Commented Oct 19, 2017 at 8:06
  • 4
    You need to put a delimiter after the \left, such as \left*(, on the third last line -- and then you will need a matching \right).
    – user30471
    Commented Oct 19, 2017 at 8:06
  • 1
    Off-topic: You may want to look into updating your TeX distribution. MikTeX2.8 hasn't been updated in several years. Do yourself a favor and download and install MikTeX2.9.
    – Mico
    Commented Oct 19, 2017 at 8:23

1 Answer 1

4

The \left directive in the row immediately before \end{multline*} doesn't look like it's needed. If it's omitted, the error message goes away. Note that \left and \right need to be followed either by a "delimiter" -- such as (, [, ), and ] -- or by a . ("period", "full stop").

I would also recommend you look into using an align* environment instead of a multline* environment.

A full MWE (with a pair round parentheses added in the first row, a macro called \abs defined via \DeclarePairedDelimiter, and the document class option 12pt repositioned):

enter image description here

\documentclass[12pt]{amsart}
\usepackage{mathtools, amsthm, amscd, amssymb, amsfonts}
\usepackage{environ}
\DeclarePairedDelimiter{\abs}{\lvert}{\rvert}
\begin{document}

\begin{align*}
\abs[\Big]{\frac{e}{e-1}(e^z-1)}
&\leq \frac{1}{2}e^{\abs{z}} + (1-\mu)(e^{\abs{z}}-1) % w/ extra parens
      + \frac{\mu\pi}{\pi^2-1} \sinh(\pi\abs{z}) 
      + \frac{\mu}{\pi^2-1} (\cosh(\pi\abs{z})-1) \\
&\leq \frac{1}{2}e^{\abs{z}} + (1-\mu)(e^{\abs{z}}-1 )
      + \frac{\mu}{\pi-1}\sinh(\pi\abs{z}) \\
&\leq \frac{\pi-2}{2\pi}e^{\abs{z}}
      + \frac{1}{\pi-1}(e^{\pi\abs{z}}-1) \\
&\leq \frac{2}{\pi-1}(e^{\pi\abs{z}}-1)
\end{align*}

\end{document} 

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