ref: 8d2b84747b1cbc54d6f23cc461d3ef838c1dfec9
dir: /sys/src/libc/port/tanh.c/
#include <u.h>
#include <libc.h>
/*
tanh(arg) computes the hyperbolic tangent of its floating
point argument.
sinh and cosh are called except for large arguments, which
would cause overflow improperly.
*/
double
tanh(double arg)
{
if(arg < 0) {
arg = -arg;
if(arg > 21)
return -1;
return -sinh(arg)/cosh(arg);
}
if(arg > 21)
return 1;
return sinh(arg)/cosh(arg);
}