Following is the source code for math functions Absolute Value, Sin, Cos, Tan, and ArcTan:

#include <math.h>
main()
{
        printf("%d %d\n",abs(-4),abs(5));
        printf("%f %f %f\n",sin(1/6.0*M_PI),cos(1/6.0*M_PI),tan(1/6.0*M_PI));
        printf("%f\n",atan(0.5)*180/M_PI);
}