javascript画圆

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圆的参数方程 x=a+r cosθ y=b+r sinθ (a,b)为圆心坐标 r为圆半径 θ为参数

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"> <head>  <title> new document </title>  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />  <style>    span{position:absolute; color: red}  </style> </head> <body> </body> <script type="text/javascript"> //<![CDATA[    var showCircle = function() {        var PI = Math.PI;        return {            draw: function(r/*半径*/, _x/*x轴偏移*/, _y/*y轴偏移*/) {                // 获得x y坐标                var x, y;                for(var i = 0; i < 360; i += 6) {                    x = Math.cos(PI / 180 * i) * r + _x;                    y = Math.sin(PI / 180 * i) * r + _y;                    var O = document.createElement('span');                    O.appendChild(document.createTextNode('.'));                    document.body.appendChild(O);                    O.style.left = x + 'px';                    O.style.top = y + 'px';                }                    }        }    }();    showCircle.draw(100, 400, 200); //]]> </script></html>