<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<script type="text/javascript">
function math1()
{
var m=Math.floor(Math.random()*100+1);
document.getElementsById("n1").value = m;
}
function cp()
{
var r=document.math1.n1.value;
if(isNaN(r)==false && r.length!=0)
{
var C,S;
C=2*Math.PI*parseFloat(r);
S=Math.round(C*100)/100;
doucument.math1.n2.value= C.toFixed(2);
doucument.math1.n3.value=C;
}
else
alert("请输入半径,必须为数字");
}
</script>
</head>
<body>
半径:<input name="n1"type="text" id="n1"><br>
周长:<input name="n2" type="text"><br>
面积:<input name="n3" type="text"><br>
<input name="s1" type="button" value="随机按钮" onclick="math1()">
<input name="s2" type="button" value="计算" onclick="cp()">
</body>
</html>