You found $\displaystyle{{\sec{{39}}}}^{\circ}\usepackage{cmbright}\Huge\$ . Remember that sine is the reciprocal of cosecant, not cosine. Use your calculator to find $\displaystyle{{\sin{{39}}}}^{\circ}\approx{0.629320391}\usepackage{cmbright}\Huge\$ . Then find the reciprocal of this and round off.