MathJax equivalent of `<strike></strike>` I recently tried to edit an old question x-th moment method that had got bumped to the front page for other reasons. The post had an equation that was meant to be, and maybe at one point was, struck through, but it no longer is. That is, the source says `<strike></strike>`, but the rendered code has no strike-through. I tried `~~~~` and `<s></s>`, without luck, and eventually (since it seemed worse to have a known-wrong equation in the text without explicit indication) deleted it; but clearly this is not the best solution. How does one strike through in MO's flavour of Markdown? EDIT: On experimentation, it seems to be about MathJax, not MarkDown: ~~1 + 1 = 2~~ versus ~~$1 + 1 = 2$~~ (both surrounded by `<strike></strike>`). Is there a way to strike through an equation?

Yes, there is `\require{cancel}\cancel{1+1=2}`$$\require{cancel}\cancel{1+1=2}$$ and `\require{enclose}\enclose{horizontalstrike}{1+1=2}`$$\require{enclose}\enclose{horizontalstrike}{1+1=2}$$ There are some other options in the "Crossing things out" answer on the MathJax reference page of Math.SE (takes a while to load, so here's a screenshot.)

`\require` works like `\usepackage`. It seems that unlike `\
ewcommand`, we only require one `\require` command for the whole page, but I'm not sure. We should probably refrain from this command in titles (though this is probably more an issue for `\
ewcommand`.)