Thanks spo much!
So according to that
to find the angle btw planes (011) and (001) in a cubic crystal (they are perpendicular) I need to normalize vectors.
Normalizing vectors:
ll v ll = sqrt( 0^2 +1^2+1^2)= sqrt(2)
llwll = sqrt (0^2 + 0^2 +1^2)= 1
v vector normalized:
x/1.41=...