# Reversed letters in a mathematical formula

Possible Duplicate:
Rotating a letter

For a work in logic, I need to write a iota upside down in a mathematical formula. I found this suggestion on the internet. First include [the usual math package] and the graphicx package

\usepackage{amsmath, amscd, amsthm, amssymb, mathrsfs,amsfonts}
\usepackage{graphicx}

in the preamble. Then use the command

\rotate{180}{\$\iota\$}

Indeed it works, but not perfectly: the axis of the rotation is at the basis of the letter (in 'normal' position). Hence, when I use this command, the reversed iota appears on a lower level than the text. I am thus not satisfied with this.

Does anyone have a better suggestion?

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\rotate[c]{180}{\$\iota\$} –  Seamus Jul 13 '11 at 11:29
For more information, see this question: tex.stackexchange.com/q/18157/215 –  Seamus Jul 13 '11 at 11:29
Sorry, that should say origin=c not c... –  Seamus Jul 13 '11 at 11:32
@Seamus:OK, that's works perfectly with \rotatebox[origin=c]{180}{\$\iota\$}. Thanks! –  Thomas Connor Jul 13 '11 at 11:35
This thread latex-community.org/forum/viewtopic.php?f=46&t=5269 also talks of rotating iota and the solutions are different from yours. –  N.N. Jul 13 '11 at 11:36

A reference is Rotating a letter, but rotating math symbols requires some more care:

\rotatebox[origin=c]{180}{\$\iota\$}}

The \$ 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:

\newcommand{\rotatediota}{{\mathpalette\rotiota\relax}}
\newcommand{\rotiota}[2]{\rotatebox[origin=c]{180}{\$#1\iota\$}}

Now \$\rotatediota_\rotatediota\$ will have the desired result (graphicx is required, of course).

## Explanation

\mathpalette\XXX\YYY becomes

\mathchoice{\XXX\displaystyle\YYY}{\XXX\textstyle\YYY}
{\XXX\scriptstyle\YYY}{\XXX\scriptscriptstyle\YYY}

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

\newcommand{\rotatediota}{\mathrel{\mathpalette\rotiota\relax}}

## Remarks

This is also a good candidate for a command to be declared robust, if used extensively in captions or headings:

\DeclareRobustCommand{\rotatediota}{...}