C库函数 cos()

#include <stdio.h>

#include <math.h>



#define PI 3.14159265



int main () {

   double x, ret, val;

   x = 60.0;

   val = PI / 180.0;

   ret = cos( x*val );

   printf("The cosine of %lf is %lf degrees\n", x, ret);



   x = 90.0;

   val = PI / 180.0;

   ret = cos( x*val );

   printf("The cosine of %lf is %lf degrees\n", x, ret);



   return(0);

}