You may have recognized that the given graph is symmetric about the y-axis, as is the graph of $\displaystyle{y}={\cos{\theta}}\usepackage{cmbright}\Huge\$ . However, the given graph has a valley with the y-axis running through it, while the graph of $\displaystyle{y}={\cos{\theta}}\usepackage{cmbright}\Huge\$ has a hill with the y-axis running through it.