css画几何图
三角形：https://jingyan.baidu.com/article/08b6a591a3208914a809222f.html
半圆：https://jingyan.baidu.com/article/9f7e7ec0bdb4b06f281554c5.html
鹰嘴：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style>
.border{
width: 3em;
height: 10em;
border: 1.1em solid;
border-top-left-radius: 100% 28%;
border-left-width: 0em;
border-right-width: 0;
border-bottom-width: 0;
border-top-color: black;
}
</style>
</head>
<body>
<body>
<div class="border"></div>
</body>
</html>
