The wedge is given an acceleration to the left.

$ \therefore $ The block has a pseudo acceleration to the right, pressing against the wedge because of which the block is not moving.

$ \therefore $ mgsin$\theta $ = macos$\theta $

or $$a = {{g\sin \theta } \over {\cos \theta }}$$

Total reaction of the wedge on the block is N = mgcos$\theta $ + masin$\theta $.

$$ \Rightarrow N = mg\cos \theta + {{mg\sin \theta \sin \theta } \over {\cos \theta }}$$

$$ \Rightarrow N = {{mg\left( {{{\cos }^2}\theta + {{\sin }^2}\theta } \right)} \over {\cos \theta }} = {{mg} \over {\cos \theta }}$$