This graph has the hill and valley shape of a sine function, so $\displaystyle{y}={a}{\sin{{b}}}{x}\usepackage{cmbright}\Huge\$ . The amplitude is 2. It has the same orientation as the graph of $\displaystyle{y}={\sin{{x}}}\usepackage{cmbright}\Huge\$ and therefore $\displaystyle{a}={2}\usepackage{cmbright}\Huge\$ .

Now there are 6 cycles shown on the interval $\displaystyle{\left[{0},{4}\pi\right]}\usepackage{cmbright}\Huge\$ , or 3 cycles on the interval $\displaystyle{\left[{0},{2}\pi\right]}\usepackage{cmbright}\Huge\$ . This tells you that $\displaystyle{b}={3}\usepackage{cmbright}\Huge\$ . So this could be the graph of $\displaystyle{y}={2}{\sin{{3}}}{x}\usepackage{cmbright}\Huge\$ .