cos, cosf, cosl - cosine function
#include <math.h>
double cos(double x);
float cosf(float x);
long double cosl(long double x);Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
These functions return the cosine of x, where x is
given in radians.
On success, these functions return the cosine of x.
If x is a NaN, a NaN is returned.
If x is positive infinity or negative infinity, a domain
error occurs, and a NaN is returned.