_rotation is measured in degrees in Flash, but circular functions like cos, sin and tan use radians. So I don't think it is a radian/ degree problem. Are you sure you can access r? Did you try the simple debug trace (r) in an enterFrame?
About radians and degrees: both measure angles, and there is a very simple equivalence between the 2 units: a full circle is 360 degrees and 2*pi radians. So 1 radian=180/pi degrees. Radians are very practical to write stuff when you do a bit of math, but they are the same, really.
Last smoke by Ilyas : yesterday at 11:45 PM.