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.

Instead of choosing the lowest point, you chose the point that is farthest to the left.

The correct range is $\displaystyle-{1}\le{y}\le{0}\usepackage{cmbright}\Huge\$ , and the correct lowest point is $\displaystyle{\left(-\frac{\pi}{{2}},-{1}\right)}\usepackage{cmbright}\Huge\$ .