Can you say what angle is made by the two red lines drawn on two sides of the cube as shown in the illustration?

The angle isn't necessarily 60 degrees if you're thinking in terms of 3-D...there's no way it can be an equilateral triangle on the corners of a cube since the beginning points of both lines are further in distance than the red lines themselves so there's no way it's an equilateral triangle if you actually count the fact that the lines are each against a different plane. The answer is 90 degrees since each line makes a 45-45-90 triangle within each face of the cube...add them together to get 90.

Posted by mike on 2004-08-04 09:02:52