Cos function returns cosine of an angle(in radian).
1 radian = 57.2958(approximately).
Declaration: double cos(double);
C program
#include <stdio.h>
#include <math.h>
#include <math.h>
int main()
{
double result, x = 1.0471;
result = cos(x);
printf("cos(%.4lf) = %.2lf\n", x, result);
return 0;
}