hdu2671

/*
分析：
    计算几何，水。

                                2013-06-25
*/

#include"iostream"#include"cstdio"#include"cmath"#include"cstring"using namespace std;int main(){int T;double k,k2,b,b2;double x1,y1,x2,y2,x,y,xx,yy;double tx,ty,dirx,diry;double X1,Y1,X2,Y2,j1,j2;cin>>T;while(T--){cin>>k;scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x,&y);b=y-k*x;//向量判断异侧xx=x+1;yy=k*xx+b;X1=x-xx;Y1=y-yy;X2=x1-x;Y2=y1-y;j1=X1*Y2-X2*Y1;X2=x2-x;Y2=y2-y;j2=X1*Y2-X2*Y1;//如果同侧，找对称点if(j1*j2>0){if(k==0){if(y2>y)y2=y-(y2-y);elsey2=y+(y-y2);}else{k2=-1/k;b2=y2-k2*x2;tx=(b-b2)/(k2-k);ty=k2*tx+b2;dirx=x2-tx;diry=y2-ty;x2=tx-dirx;y2=ty-diry;}}printf("%.2lf\n",sqrt(pow(x1-x2,2)+pow(y1-y2,2)));}return 0;}