Details

The "show" control lets you toggle the angle, axis, and viewing box. The "drag... twist" slider controls the angular position of an intermediate copy as it rotates back to the original. The "back" button puts the object back into its original position. The "snap" button moves the original to the currently rotated position. The "reset" button resets the configuration to the initial state.

Euler's rotation theorem states that every 3D motion that keeps (at least) one point fixed is a rotation. For more detail, see [1]. Suppose the object is rotated about the axis through an angle . This Demonstration defines the inverse operation that, given the attitudes of two objects with a common center, returns the angle and axis such that the second attitude is obtained from the first by rotating the latter about axis over angle .

This Demonstration also illustrates how to use the dynamically updated ViewPoint and ViewVertical in order to show the original object in a fixed position, while you drag the object.

Reference

[1] Wikipedia. "Euler's Rotation Theorem." (Nov 14, 2014) en.wikipedia.org/wiki/Euler's_rotation _theorem.