Angular Acceleration of Links in Four Bar

[god_is_atheist]

I know that I can not do the cross product to find the acceleration and angular velocity as with previous problems.
I drew the vectors to solve. I was not able to make sense of it. It seems simple but I had to use youtube.

 

[blamocur]

Is [imath]\alpha_1[/imath] the angular acceleration of B?

 

[blamocur]

Here is what I'd do to compute the acceleration for C: write an equation for the dependency between B and C, or, rather between 4 variables [imath]x_B,y_B,x_C, y_C[/imath]. When you differentiate this dependency once you'll get an equation for the speeds of B and C; differentiating it again you'll get one for the accelerations of those two points. Speed and acceleration for B are computable relatively easily, then use your equations to get the same for C.
Something similar should work for the remaining questions of this problem.