You may have miscalculated the effect of the $\displaystyle+\frac{\pi}{{2}}\usepackage{cmbright}\Huge\$ on the graph of sine. It will shift the graph of $\displaystyle{y}={\sin{\theta}}\usepackage{cmbright}\Huge\$ to the left by $\displaystyle\frac{\pi}{{2}}\usepackage{cmbright}\Huge\$ units. So the graph of $\displaystyle{y}={\sin{{\left(\theta+\frac{\pi}{{2}}\right)}}}\usepackage{cmbright}\Huge\$ will be the same as the graph of $\displaystyle{y}={\cos{\theta}}\usepackage{cmbright}\Huge\$ . This does not match the given graph.