You may have correctly determined that the reference angle is $\displaystyle{{30}}^{\circ}\usepackage{cmbright}\Huge\$ and found $\displaystyle{{\sec{{30}}}}^{\circ}\usepackage{cmbright}\Huge\$ , but you made a mistake with the sign. Use the signs of x and y in the fourth quadrant to determine the sign of secant, remembering that: $\displaystyle{\sec{\theta}}=\frac{{1}}{{x}}\usepackage{cmbright}\Huge\$