Angle of Repose(α):
It is the maximum angle of inclined plane on which body tends to move down the plane because of its own weight. Consider the equilibrium of body when body is just on point of slide.
Resolving all the forces which are parallel and perpendicular to plane, we have:
µ R = W.sina
R = W.cosa
Dividing 1 by 2 we get Tana µ
But µ = tanθ , θ= Angle of friction
That is θ =α
The value of angle of repose is same as value of the limiting angle of the friction.