If you add a positive constant c to the input of a function, that will have the effect of shifting the graph of the original function to the left by c units. Because $\displaystyle\frac{\pi}{{2}}\usepackage{cmbright}\Huge\$ is being added to the input, the graph of $\displaystyle{y}={\sin{\theta}}\usepackage{cmbright}\Huge\$ gets shifted to the left by $\displaystyle\frac{\pi}{{2}}\usepackage{cmbright}\Huge\$ units.