Answer
Sailing speed is $7.4\ \text{knots}$ at an angle of ${{85}^{{}^\circ }}$ to the $10\ \text{knots}$ wind.
Work Step by Step
With the given polar coordinate, $\left( 7.4,{{85}^{{}^\circ }} \right)$ we can derive that the sailing speed is $7.4\ \text{knots}$ at an angle of ${{85}^{{}^\circ }}$ to the $10\ \text{knots}$ wind.
