Dynamics problem: Crankshaft angular speed?

[ramzerimar]

Homework Statement

Homework Equations

Kinematic theorems:

The Attempt at a Solution

Ok, I'm trying to use another angle, phi, and find some relation between phi and theta so I can derive the equation for the angular velocity of rod B with respect to S, but I'm stuck at that point. How should I proceed with this problem?

 

[Nidum]

Hint : Use the x y coordinates of the crank pin .