So the problem is:

http://www.imathas.com/cgi-bin/mimet...ht%29%7D%7D%7D

Find the amplitude, period and phase shift and then graph the function.

http://www.imathas.com/cgi-bin/mimet...C%7D%3D%7B2%7D

http://www.imathas.com/cgi-bin/mimet...ight.%7D%7D%7D

http://www.imathas.com/cgi-bin/mimet...%5Cright%29%7D

So the answer in the book has these answers as http://www.imathas.com/cgi-bin/mimet...D%7B%7B6%7D%7D

My question is, where did the negative come from for the phase shift?