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<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport"
content="width=device-width,initial-scale=1.0">
<meta http-equiv="X-UA-Compatible"content="ie=edge">
<title>Document</title>
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<body>
<script src="./Untitled-1.js">
</script>
</body>
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var r =prompt("请输入圆的半径")
var dec1 = "数据数据输入格式错误，请重新输入！"
var dec2 = "数据类型符合要求，点击确定计算结果。"
var flag = isNaN(r)?dec1:dec2;
alert(flag);
var R = r*1;
var C = 2*Math.PI*R;
var S = Math.PI*(R**2);
document.write("圆的周长："+C.toFixed(2));
document.write("圆的面积："+S.toFixed(2));
