Integrating csch^2(x) gives an incorrect result



On Fri, 24 Jun 2011, Frazer Williams wrote:
>    (%i3) integrate((1/sinh(x))^2,x);
>                                           4
>    (%o3)                            -------------
>                                         - 2 x
>                                     2 %e      - 2
>
> According to a book of tables, the integral should be
>
>                    -coth x
The two results differ by a constant, and therefore both are equally 
correct.

Andrey