ref: 12ad6dffeb56a2ac3b63c13528534767d57d03e7
dir: /sys/src/ape/lib/ap/math/tanh.c/
#include <math.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);
}