double tanh(double);

Returns hyperbolic tangent of a radian angle x.

#include <iostream> /* including standard library */
#include <cmath> /* including math library */
 
using namespace std;
int main( void )
{
    double x;
    x = log(42);
 
    //cout.setf(ios::fixed, ios::floatfield);
    cout.precision(8);
 
    cout << "hyperbolic tangent of 42 is " << tanh (x) << endl;
    return 0;
}

 hyperbolic tangent of 42 is 0.99886686