POJ 1673 EXOCENTER OF A TRIANGLE(垂心)

题目链接

折腾了半天，没想出怎么证明，以前初中老师教过，不知道怎么办，就量量。。。受不了，怒抄模版1Y。。。

 #include <cstdio>
 #include <iostream>
 using namespace std;
 #define eps 1e-8
 struct point
 {
     double x,y;
 };
 struct line
 {
     point a,b;
 };
 point intersection(line u,line v)
 {
     point ret = u.a;
     double t = ((u.a.x-v.a.x)*(v.a.y-v.b.y)-(u.a.y-v.a.y)*(v.a.x-v.b.x))
     /((u.a.x-u.b.x)*(v.a.y-v.b.y)-(u.a.y-u.b.y)*(v.a.x-v.b.x));
     ret.x += (u.b.x-u.a.x)*t;
     ret.y += (u.b.y-u.a.y)*t;
     return ret;
 }
 point perpencenter(point a,point b,point c)
 {
     line u,v;
     u.a = c;
     u.b.x = u.a.x - a.y + b.y;
     u.b.y = u.a.y + a.x - b.x;
     v.a = b;
     v.b.x = v.a.x - a.y + c.y;
     v.b.y = v.a.y + a.x - c.x;
     return intersection(u,v);
 }
 int main()
 {
     int t;
     point a,b,c;
     scanf("%d",&t);
     while(t--)
     {
         scanf("%lf%lf%lf%lf%lf%lf",&a.x,&a.y,&b.x,&b.y,&c.x,&c.y);
         a = perpencenter(a,b,c);
         printf("%.4f %.4f\n",a.x+eps,a.y+eps);
     }
     return ;
 }