Subversion Repositories planix.SVN

#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);
}