# [Tex/LaTex] How should I write arctanh?

best practicesmath-mode

Possible Duplicate:
Define additional math operators to be typeset in roman

If I want to use the function sin in LaTeX, I write $\sin x$ or $\sin(x+1)$. If I want to use the function arctanh, I can't use $\arctanh x$:

! Undefined control sequence.
<argument> ...\ (\cos x)' &= -\sin x \\ (\arctanh
x)' &= \frac {1}{\sqrt {1 ...
l.74 \end{align*}

?
! Emergency stop.


What should I use instead for arctanh?

I thought of $\text{arctanh} x$, but this doesn't leave a space after arctanh. Additionally, it seems to be semantically incorrect, as arctanh is not "only" text.

\text is not well suited for this, use
\usepackage{amsmath}

then \arctanh behaves like \tan and friends