Hi there, I'm writing a computer program and I'm having a problem with the geometry. I would be very grateful for any help.

My problem is that i have one fixed point on a circles perimeter and one point which is moving around the perimeter. Do you know how i can calculate the distance between the points at any time? I should add that i know the radius and the angle at which the moving point is in relation to the fixed. Does such a formula exist?

Anyway, thanks for your time and any help would be amazing!