#include <time.h>
double cos (double x);
float cosf(float x);
cos() computes the principal value of the cosine of x. Express x in radians.
The cosine cos(x).
acos() and acosf()
asin() and asinf()
atan() and atanf()
atan2() and atan2f()
sin() and sinf()
tan() and tanf()