Javascript rotation in a plane

Rotate

var rotate = function(x, y){   

	var rx = 0;
	var ry = 0;

	var quarter = end/(Math.PI/2)

	console.log("rotation: " + end)

	if(end === 0)
	{
		rx = x;
		ry = y;
	}
	else if(quarter - Math.PI/2 < 0.001)
	{
		if(quarter - Math.PI/2 < 0.001)
		{
			rx = centerX;
			ry =centerY + radius;
		}
		else if(quarter - Math.PI < 0.001)
		{
			rx = centerX - radius;
			ry = centerY;
		}
		else if(quarter - 1.5 * Math.PI < 0.001)
		{
			rx = canvas.width/2 - centerX;
			ry = canvas.height/2 - centerY;
		}
		else if(quarter - 2 * Math.PI/2 < 0.001)
		{
			rx = centerX;
			ry = radius, centerY;
		}
	}
	else{
		rx = Math.abs(x*Math.cos(end) - y*Math.sin(end));
		ry = Math.abs(y*Math.cos(end) + x*Math.sin(end));
	}
	return [rx,ry]
};