JSFiddle - React, Tailwind, and code Playground

HTML

<div class="main">
  <div class="triangles"></div>
</div>

CSS

.main{
  maxw-width: 100%;
  height: 200px;
  background-color: blue;
  position: relative;
}
.triangles{
  width: 0;
    height: 0;
    position: absolute;
    bottom: 0;
    left: 0;
    border-top: 10vh solid transparent;
    border-right: 50vw solid white;
    border-left: 50vw solid white;
}