This graph has the general shape of a sine function, so $\displaystyle{y}={a}{\sin{{b}}}{x}\usepackage{cmbright}\Huge\$ . The amplitude is 4. It does not have the same orientation as the graph of $\displaystyle{y}={\sin{{x}}}\usepackage{cmbright}\Huge\$ . Because a reflection has taken place, $\displaystyle{a}=-{4}\usepackage{cmbright}\Huge\$ .

Now there is 1 cycle shown on the interval $\displaystyle{\left[-{3}\pi,{3}\pi\right]}\usepackage{cmbright}\Huge\$ , so the period is $\displaystyle{6}\pi\usepackage{cmbright}\Huge\$ . Therefore, $\displaystyle{6}\pi=\frac{{{2}\pi}}{{\left|{b}\right|}}\usepackage{cmbright}\Huge\$ . It follows that you could have $\displaystyle{b}=\frac{{1}}{{3}}\usepackage{cmbright}\Huge\$ . So this could be the graph of $\displaystyle{y}=-{4}{\sin{{\left(\frac{{1}}{{3}}{x}\right)}}}\usepackage{cmbright}\Huge\$ .