UVA10250 - The Other Two Trees

问题描述

思路

已知对任意平面向量AB=（x,y）,把向量AB绕其起点沿逆时针方向旋转角a得到向量AP=(x*cosa-y*sina,x*sina+y*cosa).

代码

#include <iostream>
#include <cstdio>
using namespace std;
int main()
{
double x1,y1,x2,y2,x3,y3,x4,y4,x,y;
while(cin>>x1>>y1>>x2>>y2)
{
if(x1==x2&&y1==y2)
cout<<"Impossible.\n";
else
{
x=(x1+x2)/2.0;
y=(y1+y2)/2.0;
x1-=x;
x2-=x;
y1-=y;
y2-=y;      //以原点为起点进行旋转
x3=-y1;
y3=x1;
x4=-y2;
y4=x2;
printf("%lf %lf %lf %lf\n",x3+x,y3+y,x4+x,y4+y);
}
}
return 0;
}