In Triangle ABC, AC = BC and mC = 62°. The longest side of the triangle is:

If angle C had been 60°, then we would have an equilateral triangle and all sides would have been equal. But, since angle C > 62, the side opposite C must be the greatest.

(the largest side is opposite the largest angle)

To determine the longest side of Triangle ABC, we need more information such as the lengths of the sides or additional angle measurements. Without this information, we cannot determine the length of the longest side.