The amplitude and the period for this function match those of the graph, but you did not check the orientation. The graph of $\displaystyle{y}={\sin{{x}}}\usepackage{cmbright}\Huge\$ has a valley to the left of the y-axis and a hill to the right. These are reversed on the graph shown, so a reflection has taken place. This has an effect on the coefficient. The correct answer is $\displaystyle{y}=-{4}{\sin{{\left(\frac{{1}}{{3}}{x}\right)}}}\usepackage{cmbright}\Huge\$ .