hdu 5476 (计算几何)

题意：求三角形内∠MPB+∠APC=∠MPC+∠APB的轨迹长度- -

1.基于M的中垂线       2.三角形内的圆弧（比赛只有看自己能否猜中），ps.以下是别人家的证明

#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <time.h>
using namespace std;
typedef long long ll;

int main()
{
    int T;
    scanf("%d",&T);
    int cas = 1;
    while(T--)
    {
        double a1,a2,b1,b2,c1,c2;
        scanf("%lf%lf%lf%lf%lf%lf",&a1,&a2,&b1,&b2,&c1,&c2);

        double Tab = (a1-b1)*(a1-b1)+(a2-b2)*(a2-b2);   //ab
        double ab = sqrt(Tab);

        double Tbc = (b1-c1)*(b1-c1)+(b2-c2)*(b2-c2);    //bc
        double bc = sqrt(Tbc);

        double h = sqrt(Tab - Tbc/4);
        double angle = acos(bc / (ab*2.0));
        double R = bc / sin(angle);

        double ans = 0;
        ans = ans +h + R*angle;
        printf("Case #%d: %.4f
",cas++,ans);
    }
}