SVG polygon with percentage units

http://codepen.io/Pavhan/pen/fnKHh

HTML

<svg viewBox="0 0 100 100" preserveAspectRatio="none" width="100%" height="100%">
  <polygon points="100,100 50,50 100,100" style="border-top: 1px solid #000; fill: #ccc;"/>
</svg>

CSS

body {
    margin: 0;
    background: white;
}