Find four points of rotated rectangle

[lordofduct]

function getRotatedRectPoint( angle:Number, point:Point, rotationPoint:Point = null):Point
{
	var ix:Number = (rotationPoint) ? rotationPoint.x : 0;
	var iy:Number = (rotationPoint) ? rotationPoint.y : 0;
	
	var m:Matrix = new Matrix( 1,0,0,1, point.x - ix, point.y - iy);
	m.rotate(angle);
	return new Point( m.tx + ix, m.ty + iy);
}

Use matrices, it makes it a lot faster and easier.

angle is in radians
point the corner's position you are finding.
rotationPoint - position in the rectangle when not rotated to be rotating around... if you don't include a rotationPoint and leave it null, it rotates around (0,0), or the upperleft corner.

so for instance a rectangle rotated around (0,0) with width = 100, and height = 50, and rotated 90 degrees:

var upperRight:Point = getRotatedRectPoint( Math.PI / 2, new Point(100,0));
var lowerRight:Point = getRoatedRectPoint(Math.PI / 2, new Point(100,50));
var lowerLeft:Point = getRotatedRectPoint(Math.PI / 2, new Point(0,50));