jsp求一个正数的平方根（法1：使用include指令）
主页面t1.jsp
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>include指令</title>
</head>
<body bgcolor="rgb(199, 237, 204)">
<div style="text-align:center">
<h1>请输入一个正数，单击按钮求这个数的平方根。</h1>
<hr>
<%@ include file="t1_ok.jsp"%>
</div>
</body>
</html>辅页面t1_ok.jsp
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<%
double num = 0;
String str=request.getParameter("num");
try{
if(str!=null){
num = Double.parseDouble(str);
}else{
out.println("【提示：】请输入数据，谢谢！");
}
} catch(Exception e){
out.println("只能输入数字") ;
}
%>
<p>请输入一个数字，谢谢！</p>
<form action="#" method="post" name="form">
<input type="text" name="num"><br><br>
<input type="submit" name="submit" value="开始计算">
</form>
<p><%=num%>的平方根是:<%=Math.sqrt(num)%></p>
</body>
</html>
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