We were asked to form the transformation matrix that rotates the x1 axis of a rectangular coordinate system 60 degrees toward x2 and the x3 axis. The thing is, I don't understand what it meant by rotating one axis toward the two other. Like, do I rotate x1 60 degrees toward the x2-x3 plane or does it mean something else? I tried to rotate x1 to the x2-x3 plane but I can never be sure of the angle between x1' and x2, and x1' and x3. How do I find the angles?