Something I Didn't Understand in this Unit.

I had a hard time trying to understand question #29 in the assignment booklet :
                      cos(a+B)*tan(a+B)
                      sin(a+B)
When Kyle did the question on the board in class I realized that tan(a+B) was the same as:
                   sin(a+B)
                   cos(a+B)
Therefore resulting in: cos(a+B)*sin(a+B) = 1
                                 sin(a+B)   cos(a+B)


Overall,  I feel like I am prepared to take the test tomorrow.