A reference is Rotating a letter, but rotating math symbols requires some more care:
$ signs are necessary, since TeX is not in math mode when it processes the contents of the box to be rotated.
If the symbol is needed also in subscripts or superscripts, some more work is needed:
$\rotatediota_\rotatediota$ will have the desired result (graphicx is required, of course).
and TeX will choose the right piece of code depending on the current math style. So it suffices to define
\XXX with two arguments, the first of which is a math style declaration. Here we don't have a "variable" part, so the second argument to
\rotiota is just
\relax (it could be any token, since it's eventually discarded;
\mathpalette requires two arguments, to begin with).
The extra group around
\mathpalette\rotiota\relax is to allow for a simpler syntax when the symbol must be used in a subscript.
If it has to be a relation symbol, don't forget to put it into
\mathrel, or modify the definition to
This is also a good candidate for a command to be declared robust, if used extensively in captions or headings:
or, loading etoolbox,