第四届省赛A题

http://acm.upc.edu.cn/problem.php?id=2217

给定逆时针序三角形两点坐标，求第三点坐标

我会告诉你我用画图画的么- -

#include <iostream>#include <cmath>#include <stdio.h>using namespace std;#define pi acos(-1.0)int main(){    int n;    cin>>n;    while(n--)    {        double x1, y1, x2, y2;        cin>>x2>>y2>>x1>>y1;                double alpha = atan2((y1-y2),(x1-x2));        double l = sqrt((y1-y2)*(y1-y2)+(x1-x2)*(x1-x2));        double x3=x2+l*cos(alpha+pi/3);        double y3=y2+l*sin(alpha+pi/3);                printf("(%.2f,%.2f)\n",x3,y3);    }}