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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


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
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
up vote 11 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:




$\Ima f\subseteq \ker g$


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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