You may have confused the effects of a and b in $\displaystyle{y}={a}{\sin{{b}}}{x}\usepackage{cmbright}\Huge\$ . The function $\displaystyle{y}={5}{\sin{{3}}}{x}\usepackage{cmbright}\Huge\$ has an amplitude of 5 and a period of $\displaystyle\frac{{{2}\pi}}{{3}}\usepackage{cmbright}\Huge\$ . The graphed function has an amplitude of 3 and a period of $\displaystyle\frac{{{2}\pi}}{{5}}\usepackage{cmbright}\Huge\$ .