Sorry to be a pest but I never got an answer and I'm really stuck Can you please check this equation.
Find polar equation of x^2 + y^2 = 10y
x^2 + y^2 = r^2
r^2 = 10sin(theta)
looks almost good to me
but, x = r sin(theta)
so we have
r^2 = 10r sin(theta)
r = 10 sin(theta)