For cubic uiu,++W1W cos pp 2 1+V1+w 1V2+n2+1 For orthorhombic uia+v,vob+wwoc cos pp (4a)2+(vb)2+(c)2y( (l2a)2+(2b)2+(2c)For orthorhombic: cos = 2 2 2 2 2 2 2 1 2 1 2 1 2 1 2 2 1 2 2 1 2 (u a) (v b) (w c) (u a) (v b) (w c) u u a v v b w w c + + + + + +  For cubic: cos = 2 2 2 2 2 2 2 1 2 1 2 1 1 2 1 2 1 2 u v w u v w u u v v w w + + + + + + 