1. The problem statement, all variables and given/known data Find Miller indexes of the vector that is vertical to the layer (211). 2. Relevant equations Unknown. 3. The attempt at a solution I'm not quite sure how to do this. The only thing I came up until now is to invert the numbers (so that I get 1/2, 1 and 1) and then find the vector that is vertical to a vector with these coordinates. But I don't think this is right at all, because this is a layer we are talking about. Not a vector.