At wikipedia this
<math>\phantom{-}\frac{8}{2}=\phantom{-}4</math>
should produce
$\phantom{-}\frac{8}{2}=\phantom{-}4$
(I dont know how to make that display correctly here either)
but I get an error message
Failed to parse (unknown function "\phantom"): {\displaystyle \phantom{-}\frac{8}{2}=\phantom{-}4 }
I have no idea whats going on. It used to work fine. What can I do to fix it.
\phantomhas been inplain.texfrom day one and it has been imported in LaTeX essentially verbatim. It is not necessary to loadamsmathfor it. On the other hand, if a JavaScript implementation of a LaTeX interpreter lacks\phantom, there's little that can be done on the LaTeX side. – egreg Jun 03 '21 at 07:38