Problem using tan() and cos() functions

I have a small bit of code that should accept an input as a double and use that input value in an equation with tan() and cos()...but it doesn't work and I don't know why. Here's my code:

Code:

`#include <stdio.h>`

#include <math.h>

int main (void)

{

double theta = 0.0, sin_theta = 0.0;

printf ("Enter a number (theta) to be calculated: ");

scanf ("%lf", &theta);

sin_theta = (tan (theta)) * (cos (theta));

printf ("Tangent of theta times cosine of theta: %lf\n\n\n",

sin_theta);

return 0;

}

Any help is welcome. Thanks!