# triple \approx and triple \approx with a straight middle line

I'm trying to create a symbol \diffeo for "diffeomorphic" and \isomet for "isometric".

I'd like it to look exactly like \approx $\approx$, but with three lines for the first one; and three lines with the middle being straight for the second one:

where approx is the symbol

.

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The first of the following macros is in the Comprehensive List of LaTeX Symbols (texdoc symbols, with TeX Live), where it is called \threesim; the second one has been built similarly.

\newcommand*{\diffeo}{%
\mathrel{\vcenter{\offinterlineskip
\hbox{$\sim$}\vskip-.35ex\hbox{$\sim$}\vskip-.35ex\hbox{$\sim$}}}}

\newcommand*{\isomet}{%
\mathrel{\vcenter{\offinterlineskip
\hbox{$\sim$}\vskip-.85ex\hbox{$-$}\vskip-.55ex\hbox{$\sim$}}}}

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I've searched Latex comprehensive symbol list before, but never found those two symbols. Don't know why they didn't add them as a built-in control and add a picture of it. I also checked Detexify (detexify.kirelabs.org/classify.html), but never got any suggestions. Thank you very much. –  Leon Lampret Jul 2 '11 at 20:15
It's on page 104, but I admit that I know where to look even without remembering the command's name. ;-) I built the second one just now. –  egreg Jul 2 '11 at 20:21