These are the highest and lowest points on the graph of $\displaystyle{y}={\sin{\theta}}\usepackage{cmbright}\Huge\$ in the interval $\displaystyle{\left[-\frac{\pi}{{2}},\frac{{{3}\pi}}{{2}}\right]}\usepackage{cmbright}\Huge\$ . The graph of cosine has a hill and valley pattern like sine, but the hills and valleys are not located in the same places.