In the cube abcd-a1b1cid1, M is the midpoint of CC1, AC intersects BD at O, and it is proved that a1o is perpendicular to the plane MBD How to prove that a1o is perpendicular to BD, BM

In the cube abcd-a1b1cid1, M is the midpoint of CC1, AC intersects BD at O, and it is proved that a1o is perpendicular to the plane MBD How to prove that a1o is perpendicular to BD, BM


It can be done in rectangular coordinates or in pure geometry
A1 projection is Ao, so A1 is vertical to BD
Because A1 is perpendicular to BM, the line is perpendicular to the plane