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I know I can use \ker in place of \text{ker} to denote the kernel of a map. Is there a similar command for the image of a map?

Even if I define my own command like

\newcommand{\Ima}{\text{Im}}

Inside the theorem environment (for example) I get the italic version of Im. How can I fix this?

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I always thought this was a huge oversight; even amsmath doesn't define it. The package does seem to have a bit of a bias toward calculus, somehow. –  Ryan Reich Dec 1 '12 at 15:25
    
@Ryan: I think part of the issue is that Im for image is less universal than ker for kernel, perhaps because Im can also be used to denote the imaginary part of a complex number. –  Charles Staats Dec 1 '12 at 15:33
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actually, \Im is already defined (in both plain tex and latex) to be a fraktur "I", so \newcommand won't work. –  barbara beeton Dec 1 '12 at 15:38
    
    
@Abramodj: Why capitalize Im and not ker? –  Bruno Le Floch Dec 2 '12 at 9:53

1 Answer 1

up vote 7 down vote accepted

You can use \DeclareMathOperator from the amsmath package to define it; in this way it will have the appropriate spacing and font:

\documentclass{article}
\usepackage{amsmath}

\DeclareMathOperator{\Ima}{Im}

\begin{document}

$\Ima f\subseteq \ker g$

\end{document}

enter image description here

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Thanks, that's great and it will be useful in many other cases! –  Abramodj Dec 1 '12 at 15:37

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