This Problem can be done in two ways.

Method 1.

Take the free body diagram of two masses.

From this a_x = g sin θ                                           …… (1)

and, m a_y = mg cos θ – N                                     …… (2)

From this Nsinθ = ma                                           …… (3)

The Mass m is in contact with M

Hence a_y = a sin θ                                               …… (4)

From eqn (1) (2) (3) & (4)

A_x = g sin θ a_y = m cos θ . sin²θ/(msin²θ + M)