Smoothing out Actionscript related movement

[knotion101]

I seem to run into probems with choppineess when I change move a movie clip with action script.. here is an example..

i have two mc's, A is stationary and B rotates around A.
here's the action script:

if (i == 360) { i = 0; }
b._x = a._x + (120 * Math.cos(i));
b._y = a._y + (120 * Math.sin(i));
i = i + .05 ;
gotoAndPlay(_currentframe