I'm hoping someone can help with this geometry problem. I keep trying, but not really getting anywhere.
In tetrahedron ABCO, angle AOB = angle AOC = angle BOC = 90^\circ. A cube is inscribed in the tetrahedron so that one of its vertices is at O, and the opposite vertex lies on face ABC. Let OA = 1, OB = 1, OC = 1. Show that the side length of the cube is 1/3.