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@(#)asinh.3 6.2 (Berkeley) 05/12/86

C 6 asinh, acosh, atanh - inverse hyperbolic functions

 #include <math.h> 

 double asinh(x)  double x; 

 double acosh(x)  double x; 

 double atanh(x)  double x; 

These functions compute the designated inverse hyperbolic functions for real arguments. These functions inherit much of their error from log1p described in exp(3M). On a VAX, acosh is accurate to about 3 \*(ups, asinh and atanh to about 2 \*(ups. An \*(up is one Unit in the Last Place carried. Acosh returns the reserved operand on a VAX if the argument is less than 1.

Atanh returns the reserved operand on a VAX if the argument has absolute value bigger than or equal to 1.

math(3M), exp(3M), infnan(3M) W. Kahan, Kwok-Choi Ng