$\displaystyle\pi\usepackage{cmbright}\Huge\$ radians corresponds to the point $\displaystyle{\left(-{1},{0}\right)}\usepackage{cmbright}\Huge\$ on the unit circle. The coordinates of this point give you the values of $\displaystyle{\cos{\pi}}\usepackage{cmbright}\Huge\$ and $\displaystyle{\sin{\pi}}\usepackage{cmbright}\Huge\$ . In particular, $\displaystyle{\sin{\pi}}={0}\usepackage{cmbright}\Huge\$ , so $\displaystyle{\left(\pi,{0}\right)}\usepackage{cmbright}\Huge\$ is on the graph of $\displaystyle{y}={\sin{\theta}}\usepackage{cmbright}\Huge\$ .