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
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<head>
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<title> new document </title>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<style>
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span{position:absolute; color: red}
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</style>
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</head>
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<body>
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<script type="text/javascript">
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//
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var showCircle = function() {
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var PI = Math.PI;
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return {
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draw: function(r/*半径*/, _x/*x轴偏移*/, _y/*y轴偏移*/) {
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// 获得x y坐标
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var x, y;
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for(var i = 0; i < 360; i += 6) {
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x = Math.cos(PI / 180 * i) * r + _x;
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y = Math.sin(PI / 180 * i) * r + _y;
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var O = document.createElement('span');
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O.appendChild(document.createTextNode('.'));
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document.body.appendChild(O);
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O.style.left = x + 'px';
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O.style.top = y + 'px';
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}
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}
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}
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}();
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showCircle.draw(100, 400, 200);
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//]]>
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</script>
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</html>
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