An interior designer has a dilemma. She has to move an amazingly heavy armchair which is up against a wall. The chair needs to be sitting so it is exactly beside its starting position and facing the same way.
If the only possible movement is to rotate the chair on any of its corners, how can the chair be moved to its new position?
Let A and B be the two corners of the chair which are against the wall.
Rotate 60 deg clockwise on corner A.
Rotate 60 deg counterclockwise on corner B.
Rotate 60 deg counterclockwise on corner A.
And, rotate 60 deg clockwise on corner B.
