What is ( -5, 2pi/3) converted into rectangular coordinates?
We have that (x, y) = (r cos θ, r sin θ) = (-5 cos (2pi/3) , -5 sin (2pi/3) ) =
( -5 (-1/2) , -5 √3/2) = [ 5/2 , -(5/2)√3 ]