Thread: What is the best way of getting clockwise angle of 2 points?

This seems to work.

Code:

#include <stdio.h>
#include <math.h>
 
#define PI 3.14159265359
 
int main()
{
    int x, y;
    // x = p2.x - p1.x;
    // y = p2.y - p2.y;
    while (1)
    {
        scanf("%d%d", &x, &y);
        double angle = asin(y / sqrt(x * x + y * y)) * (180 / PI);
        if      (x < 0) angle = 180 - angle;
        angle = 90 - angle;
        if (angle < 0) angle += 360;
        printf("%.3f\n", angle);
    }
    return 0;
}

Updated code.

Code:

#include <stdio.h>
#include <math.h>
 
#ifndef PI
#define PI 3.14159265359
#endif
 
typedef struct point { double x, y; } point;
 
double getAngleBetween(point p1, point p2)
{
    double x = p2.x - p1.x, y = p2.y - p1.y;
    double angle = asin(y / sqrt(x * x + y * y)) * (180 / PI);
    angle = x < 0 ? angle - 90 : 90 - angle;
    return angle < 0 ? angle + 360 : angle;
}
 
int main()
{
    while (1)  // ctrl-c (or eof) to quit
    {
        point p1, p2;
        printf("Enter two points: ");
        if (scanf("%lf%lf%lf%lf", &p1.x, &p1.y, &p2.x, &p2.y) != 4)
            break;
        printf("%.3f\n", getAngleBetween(p1, p2));
    }
    return 0;
}