# Does MathJax really not recognize cosec?

I tried to get the trig function cosec in MathJax, but it comes out as $$\cosec$$. In contrast, it works perfectly well for sec: $$\sec$$. Of course, one can always use \operatorname{cosec} as a workaround ($$\operatorname{cosec})$$; but this seems clumsy. The shorter form csc works: $$\csc$$. Perhaps the designers of MathJax simply don't like cosec and think that we should all switch to csc.

• This is not a bug wrt Stack Exchange software, it is a feature of mathjax, over which Stack Exchange has no control. Mathjax is not unique to some stack exchange sites. – amWhy Apr 2 '20 at 17:05
• It also recognizes $\sinh x$, but not $\sech x$. – Gerry Myerson Apr 2 '20 at 21:44
• Related (a bit): Request for Hyperbolic $\sech \,x$ inclusion in MathJax. – Martin Sleziak Apr 3 '20 at 4:51

No, you're right that mathjax doesn't recognize $\cosec(x)$: $$\cosec(x)$$, but it recognizes $\csc(x)$: $$\csc(x)$$ for use when you want to denote cosecant(x). It is likely due to the fact that \sin(x), \cos(x), \tan(x), \sec(x), \cot(x) all have three-letter operator-names, and so the choice of operator for cosecant, in mathjax, similarly has a three-letter operator: \csc(x).
Even though one can speak of $$\csc(x) = \frac 1{\sin x}$$, mathjax does not recognize $\arccsc(x)$: $$\arccsc(x)$$, though it recognizes $\csc^{-1}(x)$: $$\csc^{-1}(x)$$. But nor does it recognize $\arcsec$: $$\arcsec$$, nor $\arccot$: $$\arccot$$.
But we do have $\arcsin, \arccos, \arctan$: $$\arcsin, \arccos, \arctan$$.
Now, a work around, if you're needing to use cosecant a lot in one post, is to write \DeclareMathOperator{cosec}{cosec} before needing to use cosec. Then, you can use it as you like, as you expected you could, by writing \cosec(x). I display the results immediately below. You can click on "edit" to see that it does indeed work.
$$\DeclareMathOperator{cosec}{cosec}$$
$$\cosec(x)$$