C语言库cos()函数

#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);
}