<canvas width="600" height="400"></canvas>
<script>
function desenhaEsquadro(xa, ya, xc, yc, xa, yc, cor) {
var tela = document.querySelector('canvas');
var pincel = tela.getContext('2d');
pincel.fillStyle='black';
pincel.beginpath ( );
pincel.moveTo (50,50);
pincel.lineTo ( 50, 50, 400, 400, 50, 400, 'black');
pincel.fillStyle='whiter';
pincel.beginpath ( );
pincel.moveTo (100,175);
pincel.lineTo ( 100, 175, 100, 350, 275, 350, 'black');
</script>
