You may have made a mistake while simplifying or you may have calculated the incorrect ratio. This value is equal to $\displaystyle{{\cot{{30}}}}^{\circ}\usepackage{cmbright}\Huge\$ . To calculate tangent, use $\displaystyle{\tan{\theta}}=\frac{{y}}{{x}}\usepackage{cmbright}\Huge\$ . The correct answer is $\displaystyle\frac{\sqrt{{3}}}{{3}}\usepackage{cmbright}\Huge\$ .