#include struct point { int x, y; }; int equal(struct point *p1, struct point *p2) { if (((*p1).x == (*p2).x) && ((*p1).y == (*p2).y)) return 1; else return 0; } int quadrant(struct point *p) { if ((*p).x > 0 && (*p).y > 0) return 1; else if ((*p).x > 0 && (*p).y < 0) return 4; else if ((*p).x < 0 && (*p).y>0) return 2; else if ((*p).x < 0 && (*p).y < 0) return 3; else return 0; } int main() { int z, r; struct point *pp1; struct point *pp2; struct point *pp; struct point p1; struct poi...