点线距离：从点到线作垂线,垂线段的长就是点线距离.设点为A(m,n)；直线为y=kx+b.则垂线的斜率为-1/k,则垂线为y=-1/kx+n-km,在求直线与垂线的焦点[（n-km-b）k/ (k2+1),k2(n-kx-b)/(k2+1)+b],这样就求点点距离就可以...