atan2rad.c

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main(int argc, char ** argv)
{
	double res = 0;
	float x = 0;
	if(argc == 2)
		x = strtof(argv[1], NULL);

	res = 90.0 - x;
	if(res < 0.0)
		res += 360.0;
	res *= (M_PI/180.0);
	printf("%.2f = %.6f radians\n", x, res);
}