Animating object on a circle

Imagine you have a circle, which would vary in size ... how do you animate a sprite on the edge of a circle, even if the circle changes size realtime??

Graphics 640,480,0,2
SetBuffer BackBuffer()
radius# = 10
angle# = 0
Repeat
	angle = angle + 1.0
	radius = 50 + Sin(angle*5)*40
	Cls
	x# = 320+(Sin(angle)*radius)
	y# = 240+(Cos(angle)*radius)
	Rect x-3,y-3,7,7,True
	Oval 320-radius,240-radius,radius*2,radius*2,False
	Flip
Until KeyHit(1)

The formula for converting polar coordinates to cartesian is:

X = Radius * Cos(Angle)
Y = Radius * Sin(Angle)


So, if I want to place a circle centered at 320, 240, and place a sprite at angle 0, which is the right side of the circle, then I would go:

SpriteAngle# = 0

SpriteXOff# = CircleRadius# * Cos(SpriteAngle#)
SpriteYOff# = CircleRadius# * Sin(SpriteAngle#)

SpriteX# = 320.0 + SpriteXOff#
SpriteY# = 240.0 + SpriteYOff#


Note that 90 is the top of the circle, and that SpriteXOff# and SpriteYOff# will be negative at times, because the polar coordinate equation produces a circle centered at 0,0 in cartesian space.