Since A and B are end points of the longest chord of the circle, AB is its diameter. Hence ∠ACB = 900 as angle inscribed in a semicircle is a right angle. Thus we have Δ ABC right angled at C. Given, AC = AO = 3 cm
⇒BC=√AB2−AC2=√62−32=√27
⇒BC=3√3units ∴ Perimeter of Δ ABC=AB+BC+AC =6+3√3+3=9+3√3 units