<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
.triangle{
0;
height: 0;
border-top: 50px solid black;
border-right: 50px solid transparent;
border-left: 50px solid transparent;
}
</style>
</head>
<body>
<div class="triangle"></div>
</body>
</html>