Why isn't this working? $\require{cancel}$

$ \cancel{x} $

I copied it directly from "Crossing things out" on MathJax basic tutorial and quick reference

EDIT: It's been fixed

  • 1
    $\begingroup$ I have added the required code to the question so that the cancel works. Now all subsequent uses of \cancel on this page should work. $\endgroup$
    – robjohn Mod
    Aug 4, 2014 at 7:09

1 Answer 1


As it says in this answer, the $\LaTeX$ command \require{cancel} needs to appear in a MathJax formula before using \cancel{...}. I have added it $\underline{\text{here}}\require{cancel}$ so that the cancel in the next paragraph will render properly. Right click on the underlined "here" and choose "Show Math As > TeX Commands". You can also do the same with the cancelled $x$ in the next paragraph.

It works if you start with \require{cancel}: $\cancel{x}$

  • $\begingroup$ That actually won't work for me. I think it's a bug or something, because if I do some more MathJax below it, it just starts working! Weird. $\endgroup$ Aug 4, 2014 at 5:22
  • $\begingroup$ What do you mean it doesn't work for you? Do you not see the slashed out $x$ in my answer? If I add the requisite code to your question, I see the slashed out $x$. $\endgroup$
    – robjohn Mod
    Aug 4, 2014 at 6:09
  • $\begingroup$ I saw that Martin Sleziak added then removed the code to your question, and I saw the slashed out $x$ while it was there. $\endgroup$
    – robjohn Mod
    Aug 4, 2014 at 6:10
  • $\begingroup$ @robjohn I have only added (mathjax) tag: meta.math.stackexchange.com/posts/16489/revisions (BTW I see the slashed x rendered differently in your answer and in the question - in the questions instead of slashed x is seed red cancel.) $\endgroup$ Aug 4, 2014 at 6:54
  • $\begingroup$ @MartinSleziak: I saw the $\cancel{x}$ rendered properly after the question showed as having been edited by you, so I assumed that you had added the \require{cancel} to the question. It reverted to the red cancel before 5 minutes, so I figured you had taken it out. In any case, since the \require{cancel} is not in the question, it is not applied there. I can edit the question, but it would make the question seem pointless. $\endgroup$
    – robjohn Mod
    Aug 4, 2014 at 7:07
  • $\begingroup$ Woah I guess all this convo happened while I was sleeping. Um yeah I guess it's working now (maybe because RobJohn changed it?). It wasn't working last night. $\endgroup$ Aug 4, 2014 at 22:42
  • $\begingroup$ @Zack: did you notice the change to your question that I made to enable the \cancel? $\endgroup$
    – robjohn Mod
    Aug 4, 2014 at 23:21
  • $\begingroup$ The "\require" thing? Also how did you do a quote in a comment? The carrot ">" symbol doesn't work $\endgroup$ Aug 4, 2014 at 23:22
  • $\begingroup$ Ok I see. I selected you as my answer thanks $\endgroup$ Aug 4, 2014 at 23:34
  • $\begingroup$ @Zack: The greater-than-sign should work to quote things. Do you have an example of where it doesn't work? $\endgroup$
    – robjohn Mod
    Aug 5, 2014 at 0:01
  • $\begingroup$ It's not working here in the comments. <quote >quote $\endgroup$ Aug 5, 2014 at 0:23
  • $\begingroup$ @Zack: comments are meant to be short. You can only quote lines in a post and the '>' needs to be at the beginning of the line. See this help page. $\endgroup$
    – robjohn Mod
    Aug 5, 2014 at 0:33
  • $\begingroup$ @Zack if you mean \cancel, that is done by putting the srting in backticks. It has similar background to quotes, though it's different on HTML level, and meant for code fragments. $\endgroup$
    – user147263
    Aug 5, 2014 at 0:37
  • $\begingroup$ @Zack: what 900-sit-ups a day mentions is on the same help page here. $\endgroup$
    – robjohn Mod
    Aug 5, 2014 at 6:51

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