Originally Posted by

**rainer** Hi,

Two things regarding hyperbolic tangent (tanh(x)):

1) What is the inverse function of tanh(x)?

Apparently it is NOT artanh(x).

I need to know how to "undo" a tanh(x) function. Please help.

2) In my grapher, artanh(1) does not exist (is undefined, invalid or whatever).

Yet when I plug in artanh(sin(x)^2+cos(x)^2), which should be the same, I get weird splotches.

Is the grapher getting confused, or does there really exist a difference between 1 and sin(x)^2+cos(x)^2 vis-a-vis artanh(x)?

Thanks