I need some help, mostly related to math :P

When you set an object A at the X and Y position of another object B, and you want them to be on this place when you rotate object B, how would this expression look??? Its most likely related to Cos Sin. I have a big Map (Active Object) that I can rotate, but I want the houses, trees etc to be on the same location on the Map when its rotated. As of now, they stand still.

Any ideas?