Here is the picture: 2011-11-15_11-07-53_425.jpg picture by Bashyboy - Photobucket

The amplitude is easy enough to find--it is 3, and since it is a reflection, it is therefore -3--, but what I can't find is the coefficient for x, which is b. I understand the period to be 2pi/b, and in the answer key they are utilizing in this way: 2pi/b = pi. I don't understand, is pi the period? And if so, how am I able to deduce this from the graph?

Thank you