Mark M. answered 05/08/19
Retired math prof. Very extensive Precalculus tutoring experience.
If r = -2sinθ, then r2 = -2rsinθ.
So, x2 + y2 = -2y
x2 + (y2+2y) = 0
Complete the square to obtain x2 + (y2+2y+1) = 1
So, (x-0)2 + (y+1)2 = 1. This is a circle centered at (0,-1) with radius 1 traced out clockwise as θ increases from 0 to 2π. .
Table of values:
r 0 -2 0 2 0
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θ 0 π/2 π 3π/2 2π