效果是这样的：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>使用css transform属性画正三角形</title>
<style>
.box1,
.box1::after,
.box1::before {
width: 50px;
height: 50px;
position: relative;
background-color: red;
overflow: hidden;
float: left;
}
.box1::after,
.box1::before {
content: "";
position: absolute;
background-color: #fff;
transform-origin: bottom right;
transform: rotate(60deg) scaleX(1.2);
}
.box1::before {
transform-origin: left bottom;
transform: rotate(-60deg) scaleX(1.2);
}
.box2 {
width: 100px;
height: 20px;
display: inline-block;
background-color: lightslategray;
}
</style>
</head>
<body>
<div class="box1"></div>
<div class="box2"></div>
</body>
</html>
