js determines whether a point is within a triangle_javascript skills

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If you need to introduce external Js, you need to refresh to execute <script> function a(x,y,color) {document.write("<img border='0' style="max-width:90%"+x+"; top: "+y+";background-color: "+color+"' src='px.gif' style="max-width:90%"js determines whether a point is within a triangle_javascript skills" >")} </script>]<script> function line(x1,y1,x2,y2,color) { var tmp; if(x1>=x2) { tmp=x1; x1=x2; x2=tmp; tmp=y1; y1=y2; y2=tmp; } for(var i=x1;i<=x2;i++) { x = i; y = (y2 - y1) / (x2 - x1) * (x - x1) + y1; a(x,y,color); } } function rule(x,y) { x = x; y = y; r1 = y - 100 - (300-100)/(500-400)*(x-400); r2 = y - 300; r3 = y - 300 - (100-300)/(400-300)*(x-300); if (r1>0&&r2<0&&r3>0) { return "在三角形内！"; } else {return "不在三角形内！";} } line(400,100,500,300,"ff0000"); line(500,300,300,300,"ff0000"); line(300,300,400,100,"ff0000"); </script>