MathNet 2020 — Math Olympiad Vault — Part 05 Question 60

In the figure below, the segments $A M$, $A K$, $B_{2} C_{2}$ and $B_{1} C_{1}$ are tangent to the circle with center $O$. If $\angle B_{1} O B_{2} = 30^{\circ}$, find the measure of the angle $\angle B_{1} D B_{2}$.