I was asked the write down the Miller indices for a plane. The question is further described in http://www.wretch.cc/album/show.php?i=kenmse&b=13&f=1643363273&p=2 I took point A as an origin. For the plane "opn", the intersections with X axis and Y axis are a/2 and -a respectively. Then I really can't figure out the intersection of plane "opn" with the Z axis. Is there any one can help me with the question or just simply give me some hints? I'd really appreciate your help!!