Example 5.9.  (a)  ,  

and  (b) .  

Since these sets of solutions are not equal, Identity (5-21)  does not always hold.

Explore Solution 5.9.

First, enter    and find the principal values.

Second, find the other values in the solution sets.

Caveat.  The two solution sets are different.  Therefore, in general ,  .  

The following computation is also interesting.

Since n is an arbitrary integer, the last equation does not hold true, hence .  

(c) 2006 John H. Mathews, Russell W. Howell