Find point on me where line from my center to point p intersects my boundary. @param {number} angle If angle is specified, intersection with rotated ellipse is computed.
function(p, angle) {
	    p = point(p);
            if (angle) p.rotate(point(this.x, this.y), angle);
            var dx = p.x - this.x;
	    var dy = p.y - this.y;
            var result;
	    if (dx === 0) {
	        result = this.bbox().pointNearestToPoint(p);
                if (angle) return result.rotate(point(this.x, this.y), -angle);
                return result;
	    }
	    var m = dy / dx;
	    var mSquared = m * m;
	    var aSquared = this.a * this.a;
	    var bSquared = this.b * this.b;
	    var x = sqrt(1 / ((1 / aSquared) + (mSquared / bSquared)));

            x = dx < 0 ? -x : x;
	    var y = m * x;
	    result = point(this.x + x, this.y + y);
            if (angle) return result.rotate(point(this.x, this.y), -angle);
            return result;
        }