Explanation:
Things to recall for polar equations:
y = r sinΦ
x =r cos Φ
and r^2 = x^2 + y^2
r = 2 sin Φ Multiply both sides by 'r'
r^2 = 2 r sin Φ
recall that x^2 + y^2 = r^2
so x^2 + y^2 = 2 r sin Φ but r sin Φ is just 'y' (see above)
so x^2 + y^2 = 2 y re-arrange
x^2 + y^2 - 2y = 0 'complete the square ' for 'y'
x^2 + (y-1)^2 -1 = 0 re-arrange
x^2 + ( y-1)^2 = 1 This is the equation of a circle
with center (h,k) = (0,1) and radius '1'