The effect of adding $\displaystyle\frac{\pi}{{2}}\usepackage{cmbright}\Huge\$ to the input of the function is to shift the graph of $\displaystyle{y}={\cos{\theta}}\usepackage{cmbright}\Huge\$ to the left by $\displaystyle\frac{\pi}{{2}}\usepackage{cmbright}\Huge\$ units. This will give you a repeating hill and valley pattern with a hill just to the left of the y-axis and a valley just to the right. This describes the graph shown.