You want the inverse hyperbolic tangent function: artanh(x)
Sometimes, it's written tanh-1(x) or arctanh(x) or atanh(x).
If y = tanh(x) then x = artanh(y)
If you google keywords hyperbolic tangent function, you can find formulas for it, like this one:
artanh(x) = 1/2*ln[(1 + x)/(1 - x)]
Functions and their inverses are not "completely equivalent", but each completely determines the other.… trying to make y=tanh(x) into an equation such as x="so and so" where both equations are completely equivalent to each other.
Be careful, with inverses. They often come piecewise, like sqrt(x) and -sqrt(x), because of domain restrictions. :cool:… For example, in the equation y = x^2, if I wanted to manipulate the equation so that it because x="something", I would simply take the square root of y and x so that the equation would look like x=±sqrt(y).