版权声明：转载请先告知哦 https://blog.csdn.net/PINK789/article/details/88398866
<!DOCTYPE html>
<html>
<head>
<title></title>
<style type="text/css">
#father{width: 600px;height: 600px;background-color: yellow;}
#div{width: 0px;height: 0px;border:50px solid green;border-top-color: red;border-bottom: none;border-left-color:rgba(255,255,255,0);border-right-color:rgba(255,255,255,0);}
</style>
</head>
<body>
<div id="father">
<div id="div"></div>
</div>
</body>
</html>
