I. Given: AB = BC We can only say that ΔABC is isosceles. It may or may not be equilateral as there is no information about side CA. II. Given: ∠ABC = 600
II alone is not sufficient as one angle alone cannot completely specify atriangle. I&II. ∠ABC = 60° ⇒ ∠BAC + ∠ACB = 180°– 60° = 120° Given: AB = BC, ⇒∠BAC = ∠ACB = 60° Hence, ΔABC is equilateral. ∴ Ι&ΙΙ together are sufficient.