The lowest point is correct, but the range is not. The interval $\displaystyle-{1}\le{y}\le{1}\usepackage{cmbright}\Huge\$ is the range of the entire sine function. However, when $\displaystyle-\pi\le\theta\le{0}\usepackage{cmbright}\Huge\$ , the y-values are negative or 0. The correct range is $\displaystyle-{1}\le{y}\le{0}\usepackage{cmbright}\Huge\$ .