Stuck on trig problem

[Ike777z]

Can't seem to find first triangle to start problem.

 

[blamocur]

You can figure out the value of X from the top of the picture using only 10 for small diameters and 280. This can be done by considering the right triangle with one vertex in the center of a small circle and another at the center of the large one. Can you figure out this triangle ?