You may have recognized that there is one high point, where the sine function equals 1, and one low point, where the sine function equals $\displaystyle-{1}\usepackage{cmbright}\Huge\$ , and that they are $\displaystyle\pi\usepackage{cmbright}\Huge\$ units apart. However, you incorrectly located them along the horizontal axis. The correct answer is: when $\displaystyle\theta=-\frac{{{7}\pi}}{{2}}\usepackage{cmbright}\Huge\$ , $\displaystyle{\sin{\theta}}={1}\usepackage{cmbright}\Huge\$ ; when $\displaystyle\theta=-\frac{{{5}\pi}}{{2}}\usepackage{cmbright}\Huge\$ , $\displaystyle{\sin{\theta}}=-{1}\usepackage{cmbright}\Huge\$