For you math wizards!

Scenario:

A person steps outside a circle, and is subsequently teleported back inside it (activated in a trigger's On Deactivation field, basically). This could be done simply by moving the unit, say, 5 meters in the direction of the centre of the circle (getPos TriggerName). What math wizardy would I need to perform to be able to do this rather simple operation? I suck at math, so all I basically need is the function, explanations will be useless

(I bet it involves tan and sin and all those scary buggers).

Tried to search for this, but failed. So thanks!

Wolfrug out.