You may have thought that the effect of adding $\displaystyle\frac{\pi}{{2}}\usepackage{cmbright}\Huge\$ to the input was to shift the graph of the original function to the right, but actually it will shift to the left. So, for example, the hill with the y-axis running through it in the graph of $\displaystyle{y}={\cos{\theta}}\usepackage{cmbright}\Huge\$ becomes a hill just to the left of the y-axis in the graph of $\displaystyle{y}={\cos{{\left(\theta+\frac{\pi}{{2}}\right)}}}\usepackage{cmbright}\Huge\$ . This does not match the graph given.