Compute the Euler Axis and Angle Geometrically

Euler's Rotation Theorem states that any rigid motion that leaves the origin fixed is a rotation about an axis through the origin. Given the images x', y', z' of the three unit vectors x, y, z, (in which case {x', y', z'} constitutes a rotation matrix), there are various methods to determine the so-called Euler rotation axis and angle. This demonstration illustrates a geometric method.