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Section: Mathematical Functions
Computes the inverse hyperbolic tangent of its argument. The general syntax for its use is
y = atanh(x)
 where x is an n-dimensional array of numerical type. 
The atanh function is computed from the formula 
![\[ \tanh^{-1}(x) = \frac{1}{2}\log\left(\frac{1+x}{1-x}\right) \]](form_58.png) 
 where the log (and square root) is taken in its most general sense. 
Here is a simple plot of the inverse hyperbolic tangent function
--> x = -0.99:.01:0.99;
--> plot(x,atanh(x)); grid('on');
