You may have been thinking about the fact that $\displaystyle\theta=\frac{{1}}{{2}}\usepackage{cmbright}\Huge\$ at exactly one point. However, the question is asking about the value of $\displaystyle{\sin{\theta}}\usepackage{cmbright}\Huge\$ , not the value of $\displaystyle\theta\usepackage{cmbright}\Huge\$ . The first thing that you need to do is to look at each hill and recognize that the value of $\displaystyle{\sin{\theta}}\usepackage{cmbright}\Huge\$ goes up from 0 to 1, and then down from 1 to 0.