# How do you convert (6,-pi/5) into rectangular coordinates?

$\approx \left(4.854 , - 3.527\right)$
In general to convert the polar coordinate $\left(r , \theta\right)$ into rectangular coordinates, you just do $\left(r \cos \theta , r \sin \theta\right)$.
In the case of $\left(6 , - \frac{\pi}{5}\right)$, this would be
$\left(6 \cos \left(- \frac{\pi}{5}\right) , 6 \sin \left(- \frac{\pi}{5}\right)\right) \approx$(4.854, -3.527)#