I've come across a problem in a past paper while studying for exams, the solution is not given so I can only guess what I have to do, any guidance would be appreciated. 1. The problem statement, all variables and given/known data Calculate the Miller indices of the shaded plane with respect to the three primitive lattice vectors shown. In fig 1 and 2. 2. Relevant equations n/a 3. The attempt at a solution So figure 1 is quite obviously (1 1 1), I'm not sure how to handle figure 2. The way I was taught to calculate miller indices was pretty formulaic; Define an origin, look for intercepts with the lattice vectors, take the reciprocals and voila. I've never encountered a problem in which the lattice vectors aren't parallel to the edges of the cube and it's thrown me off a little. Is it as simple as defining another set of axes parallel to the lattice vectors and extrapolating the plane to see where it intercepts those axes?