[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.

Best Answer

\text is not well suited for this, use

\usepackage{amsmath}
\DeclareMathOperator\arctanh{arctanh}

then \arctanh behaves like \tan and friends

Related Question