<div class="treygol"></div>
<style>
  .treygol { margin: 50px; }
  .treygol { width: 0px; height: 0px;
   
   border-top: 50px solid transparent;
   border-bottom: 50px solid #000;
    
   border-right: 50px solid transparent;
   border-left: 50px solid transparent;

  }
</style>