<canvas width="600" height="400"></canvas>
<script>
var tela = document.querySelector("canvas");
var pincel = tela.getContext("2d");
pincel.beginPath();
pincel.moveTo(50, 50);
pincel.lineTo(50, 400);
pincel.lineTo(400,400);
pincel.fill();
//triangulo Interno
pincel.fillStyle = "red";
pincel.beginPath();
pincel.moveTo(100, 175);
pincel.lineTo(100, 350);
pincel.lineTo(275, 350);
pincel.fill();
</script>
