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I wanted to actually sketch a matrix and needed the flipped version of $\ \ddots\ $, but I can't find a way to do it.

Tried reflectbox iddots udots and all the crazy stuff you find somewhere at TSE.

Can somebody help me?

For everybody searching for a workaround U+22F0 $⋰$ is actually "working" but it seems a bit unloved, tiny and not well spaced compared to it's brother U+22F1 $⋱$ (This has actually to do with the math-environment)

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  • $\begingroup$ You might want to read docs.mathjax.org/en/latest/…, especially the end of that section $\endgroup$ – Peter Krautzberger May 20 '16 at 21:59
  • $\begingroup$ I don't know what font is actually used inside the math-environment and how "I" could help fixing it on a meta-global level. $\endgroup$ – Patrick Abraham May 21 '16 at 0:32
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    $\begingroup$ I can't be the only one who read "mathjax and idiots". $\endgroup$ – Najib Idrissi May 21 '16 at 6:23
  • $\begingroup$ @NajibIdrissi I actually enjoy MathJax a bunch and the whole system. That's why I don't just toss the table and try to find an easy (local) workaround, but instead the community to help me and maybe get it changed, for future users! $\endgroup$ – Patrick Abraham May 21 '16 at 9:41
  • $\begingroup$ Definitely I've observed some things that fit neatly under the heading of "MathJax and idiots", but I'm not sure they're worth posting about. $\qquad$ $\endgroup$ – Michael Hardy May 28 '16 at 7:52
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Try

\newcommand\iddots{\mathinner{
  \kern1mu\raise1pt{.}
  \kern2mu\raise4pt{.}
  \kern2mu\raise7pt{\Rule{0pt}{7pt}{0pt}.}
  \kern1mu
}}

This is based off the actual definition of \ddots in $\rm\TeX$, which constructs the character from three separate dots like this.

Then the result for \iddots is $\newcommand\iddots{\mathinner{\kern1mu\raise1pt{.}\kern2mu\raise4pt{.}\kern2mu\raise7pt{\Rule{0pt}{7pt}{0pt}.}\kern1mu}}\iddots$ rather than $\unicode{x22F0}$. Compare to \ddots: $\ddots$

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  • $\begingroup$ You did a little typo in the last line you wrote \ddots instead of \iddotsin the last line. And I thought it wasn't possible to use newcommand inside stackexchange itself. Thanks. $\endgroup$ – Patrick Abraham May 21 '16 at 11:50
  • $\begingroup$ Since I am unable to edit / view your post, I am not able to verify or repeat this. Tried it in the post itself and it straight up didn't worked. $\endgroup$ – Patrick Abraham May 21 '16 at 11:54
  • $\begingroup$ When I copy it the same way as in the quoted text in post, I get an error which says: "Extra close brace or missing open brace" (In the post preview. Not in a comment.) When I remove the last } i get: $\newcommand\iddots{\mathinner{ \kern1mu\raise1pt{.} \kern2mu\raise4pt{.} \kern2mu\raise7pt{\Rule{0pt}{7pt}{0pt}.} \kern1mu} }\iddots$ (Which is, up to the new lines, probably the same thing as in the source of your post.) $\endgroup$ – Martin Sleziak May 21 '16 at 13:05
  • $\begingroup$ @PatrickAbraham Even if you cannot edit post you should be able to see the source like this or like this. For testing, you can use and appropriate sandbox. (At least in one of the sandboxes the answers there are CW, you should probably be able to edit any of them. Or you can post a new answer in the Formatting Sandbox.) $\endgroup$ – Martin Sleziak May 21 '16 at 13:11
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    $\begingroup$ @PatrickAbraham, thanks for pointing out the typos. I've fixed them. Yes, you can use \newcommand and \def in StackExchange, through it is not encouraged because it can affect other posts. But if you are adding a missing standard command, I think people would be OK with it. $\endgroup$ – Davide Cervone May 21 '16 at 13:28
  • $\begingroup$ @MartinSleziak, thanks for the report about the extra brace. I have fixed in the post. I copied it from a working example, but missed the one at the end of the second-to-last line and thought I had missed one while copying, so added it in. Sorry for the mixup. $\endgroup$ – Davide Cervone May 21 '16 at 13:29
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    $\begingroup$ @PatrickAbraham I will add this link to accompany Davide Cervone's comment that newcommand should be used carefully here. (Mainly not in the titles.) You can probably find a few other posts discussing use of newcommand here on meta. $\endgroup$ – Martin Sleziak May 21 '16 at 13:44
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    $\begingroup$ " you can use \newcommand and \def in StackExchange, through it is not encouraged because it can affect other posts" Ouch! That's kind of a nasty threat. $\endgroup$ – Pedro Sánchez Terraf May 25 '16 at 19:15
  • $\begingroup$ @PedroSánchezTerraf, see the link in Martin's comment for a discussion of the situation and its potential solutions. $\endgroup$ – Davide Cervone May 26 '16 at 11:00
  • $\begingroup$ @DavidCervone Thanks for the pointer. $\endgroup$ – Pedro Sánchez Terraf May 26 '16 at 11:46

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