Mark M. answered 11/23/19
Retired math prof. Very extensive Precalculus tutoring experience.
A point with polar coordinates (r, θ) has rectangular coordinates (rcosθ, rsinθ) and lies on the circle with center (0,0) and radius l r l.
The given points do not lie on the unit circle. The point with polar coordinates (-6, -π/6) lies on the circle centered at (0,0) with radius 6 and has rectangular coordinates (6cos(-π/6), 6sin(-π/6)) = (6(√3/2), 6(-1/2)) = (3√3, -3). The values √3/2 and -1/2 come form the point on the unit circle corresponding to the angle -π/6.
Similarly, the point with polar coordinates (2, 3π/2) lies on the circle centered at (0,0) with radius 2 and has rectangular coordinates (2cos(3π/2), 2sin(3π/2)) = (0, -2)