Answer
$\theta=-63^{\mathrm{o}}$
($63^{\mathrm{o}}$ clockwise from the +x axis)
Work Step by Step
(d)
Continuing on the calculation of part a,
$ \displaystyle \vec{v}_{avg,AB}=\frac{\Delta\vec{r}_{AB}}{\Delta t}=\frac{(15m)\hat{i}+(-30m)\hat{j} }{300s}=\frac{(15m) }{300s}\hat{i}+\frac{-30m }{300s}\hat{j}$
$\displaystyle \theta=\tan^{-1}\frac{\frac{-30m }{300s}}{\frac{(15m) }{300s}}=\tan^{-1}(-2)=-63^{\mathrm{o}}$
($63^{\mathrm{o}}$ clockwise from the +x axis)
