Canvas How to - Draw equilateral triangle

Question

We would like to know how to draw equilateral triangle.

Answer


<!--from  www . j  a  v  a2 s  . c  om-->
<!DOCTYPE html>
<html>
<head>
<script type='text/javascript'>//<![CDATA[ 
window.onload=function(){
    var canvas = document.getElementById('canvas');
    var ctx = canvas.getContext('2d');
    drawEqTriangle(ctx, 100, canvas.width/2, canvas.height/2);
    function drawEqTriangle(ctx, side, cx, cy){
        var h = side * (Math.sqrt(3)/2);
        ctx.strokeStyle = "#ff0000";
        ctx.save();
        ctx.translate(cx, cy);
        ctx.beginPath();
        ctx.moveTo(0, -h / 2);
        ctx.lineTo( -side / 2, h / 2);
        ctx.lineTo(side / 2, h / 2);
        ctx.lineTo(0, -h / 2);
        ctx.stroke();
        ctx.fill(); 
        ctx.closePath();
        ctx.save();
    }
}//]]>  
</script>
</head>
<body>
  <canvas id="canvas" width="300" height="300"></canvas>
</body>
</html>

The code above is rendered as follows: