What is the relation between accelerations of points A and B is the given 

From the constraint relation, the accelerations of the bodies in perpendicular direction to the point of contact of the surfaces should be same.

Let the acceleration of A and B be ${\mathrm{a}}_{\mathrm{A}} \mathrm{and} {\mathrm{a}}_{\mathrm{B}}$ respectively.

The components of the acceleration along the common normal must be equal.

${\mathrm{a}}_{\mathrm{A}}\cos (90-\mathrm{\theta })={\mathrm{a}}_{\mathrm{B}}\mathrm{cos\theta }$

$\Rightarrow {\mathrm{a}}_{\mathrm{B}}={\mathrm{a}}_{\mathrm{A}}\tan \mathrm{\theta }$