平面坐标系中，求点在线上的投影坐标（如图）

已知点A(x1,y1)、B(x2,y2)、M(m,n)，求点M在线段AB上的投影坐标。

double CTrackLineView::PointToXianDuanChuiYingPointjingdu(double m, double n, double x1, double y1, double x2, double y2)
{//计算点到线垂影坐标
return
(
(m*(x2-x1)*(x2-x1)+n*(y2-y1)*(x2-x1)+(x1*y2-x2*y1)*(y2-y1))
/((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1))
);

}
double CTrackLineView::PointToXianDuanChuiYingPointweidu(double m, double n, double x1, double y1, double x2, double y2)
{//计算点到线垂影坐标
return
(
(m*(x2-x1)*(y2-y1)+n*(y2-y1)*(y2-y1)+(x2*y1-x1*y2)*(x2-x1))
/((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1))
);

}