过点(m,n)且与直线ax+by+c=0垂直的直线方程为bx-ay+an-bm=0两条直线的交点为((b^2m-abn-ac)/(a^2+b^2),(a^2n-abm-bc)/(a^2+b^2))点(m,n)到两直线交点的距离就等于点(m,n)到直线ax+by+c=0的距离d=根号{[(b^2m-abn-ac)...