Solution 4.6c
From Mechanics
Resultant force \displaystyle =80\textrm{.}9\mathbf{i}-11\textrm{.}3\mathbf{j}\ \text{N}
Thus
\displaystyle \tan \alpha =\frac{-11\textrm{.}3}{80.9}=-0\textrm{.}14
giving
\displaystyle \alpha =-8\textrm{.}0{}^\circ
As the vector is in the fourth quadrant