点与线的距离及垂足点

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点与线的距离及垂足点

<html> <head> <meta http-equiv="Content-Type" content="text/html"> <title>点与线的距离及垂足点</title> </head> <script language=javascript> function dist(x, y, startx, starty, endx, endy) { var se = (startx-endx)*(startx-endx)+(starty-endy)*(starty-endy);//线段两点距离平方 var p = ((x-startx)*(endx-startx)+(y-starty)*(endy-starty)); //向量点乘=|a|*|b|*cosA var r = p/se; //r即点到线段的投影长度与线段长度比 var outx=startx+r*(endx-startx); var outy=starty+r*(endy-starty); var des =(x-outx)*(x-outx)+(y-outy)*(y-outy); alert(outx); alert(outy); alert(Math.round(Math.sqrt(des))); } </script> <body> <input type=button value='dist' onclick="dist()"> <textarea id='textjs' rows="20" cols="120"> dist(5,20,1,6,20,15); </textarea> <br> <input type="button" value="run javacript" onclick="javascript:eval(textjs.value);"> </body> <html>

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