Length of a chord = 2rSin\(\frac{\theta}{2}\)

\(\theta\) = 60º not 30º and radius = 9cm

Therefore, Length of the chord = 2 x 9 Sin\(\frac{60º}{2}\) = 2 x 9 x Sin 30º =  2 x 9 x \(\frac{1}{2}\) = 9cm.