Determine the direction cosines for this vector these are

Question

Consider an arbitrary 3D vector: A=A_xx+A_yy+A_zz

a) Determine the direction cosines for this vector. These are cos[α], cos[β] and cos [γ], where α is the angle between A and x , where β is the angle between A and y, and γ is the angle of A and z.

b) Show that the direction cosines obey the relationship (cos[α])2+(cos[β])2+(cos [γ])2.