double sin(double);

return the sinus

compile in linux with: gcc sin.c -o sin -lm -Wall

#include <stdio.h> /* including standard library */
//#include <windows.h> /* uncomment this for Windows */
 
#include <math.h> /* including math library */
 
int main (void)
{
  double x;
  x = 42.0;
  printf ("sine of %lf° is %lf\n", x, sin(x*3.1415/80) );
  return 0;
}

 output:
 user@host:~$ ./sin 
 sine of 42.000000° is 0.996921