Advanced coordinate rotation

If you are going to be rotating objects around a point, and you are starting with just their positions, I've got a formula for you. The formula just needs the x, y position of the object in relation to the center point and the angle to rotate by. It returns the new x, y position of the object, relative to the center. Here's the basic formula:

x1 = cos(angle) * x - sin(angle) * y;
y1 = cos(angle) * y + sin(angle) * x;