Decomposition of rotational operators

Let us now consider a rotation R ah) in which h is an axis in the YZ plane and a is very small (see figure 5.2). If 6 is the angle between h and the Z axis, a rotation tinough a about h can be decomposed into a rotation through a cos 9 about Z, followed by a rotation through a sin 0 about Y (in either order to this level of approximation) so that 

A generaUsation of this result allows us to express the infinitesimal rotation operator about any axis n in the form 

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