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This question already has an answer here:

When I use \left( and \right) to get appropriately sized parentheses for an operator, a space is created between the operator and the parentheses. I think it looks bad. Is it intentional? If so, why? If not, is it easy to 'repair'?

\documentclass{article}

\usepackage{amsmath}
\usepackage[active,tightpage]{preview}
\PreviewEnvironment{align*}
\begin{document}
\begin{align*}
    \log(a) &= 0\\
    \log\left(a\right) &= 0\\
    \log\left(\frac{a}{b}\right) &= 0
\end{align*}
\end{document}

Gives the following output:

marked as duplicate by user156344, campa, Community Apr 2 at 9:15

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  • A left-right pair forms an "inner" construction, and the operator sees that as a symbol and inserts a space. Often it is better to just scale manually, using the \bigl and \bigrvariants (there are four left and four right), which also classifies as open/close and thus no space is inserted. For the autoscaled, see the mleftright package. – daleif Apr 2 at 8:54
3

Using the \mleft ...mright` pair also yields a correct spacing. Compare:

\documentclass{article}

\usepackage{amsmath}
\usepackage{mleftright}
\usepackage[active,tightpage]{preview}
\PreviewEnvironment{align*}
\begin{document}

\begin{align*}
    \log(a) &= 0\\
    \log\left(a\right) &= 0\\
    \log\mleft(a\mright) &= 0\\
    \log\left(\frac{a}{b}\right) &= 0\\
    \log\mleft(\frac{a}{b}\mright) &= 0
\end{align*}

\end{document} 

enter image description here

1

The space looks good. But if you still want to decrease the space between the operator and the parentheses, a quick method is to use a negative space, \!. It works in this way:

\documentclass{article}

\usepackage{amsmath}
\usepackage[active,tightpage]{preview}

\PreviewEnvironment{align*}

\begin{document}
\begin{align*}
    \log(a) &= 0\\
    \ \\
    \log \left(a\right) &= 0\\
    \log\!\left(a\right) &= 0\\
    \ \\
    \log\left(\frac{a}{b}\right) &= 0\\
    \log\!\left(\frac{a}{b}\right) &= 0
\end{align*}
\end{document}

The result is below.

enter image description here

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