dist(10,0,0,0,10,10);function dist(x:Number,y:Number,x1:Number,y1:Number,x2:Number,y2:Number):void{    var se:Number=(x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);//线段两点距离平方    var p:Number=((x-x1)*(x2-x1)+(y-y1)*(y2-y1));//向量点乘=|a|*|b|*cosA    var r:Number=p/se; //r即点到线段的投影长度与线段长度比    var outx:Number=x1+r*(x2-x1);//垂足x    var outy:Number=y1+r*(y2-y1);//垂足y    var des =(x-outx)*(x-outx)+(y-outy)*(y-outy);//与垂足距离    trace(outx);    trace(outy);    trace(Math.round(Math.sqrt(des)));}/*output: 5 5 7*/

\[

\overrightarrow{AB}

\]