Determine whether a Triangle with side lengths of 12, 16 and 21 is a Right Triangle

A Right Triangle must satisfy the Converse of the Pythagorean Theorem: a² + b² = c²
From the given side lengths, let a = 12, b = 16, c = 21  (c cannot be less than a or b)
a² + b² = (12)² + (16)²
a² + b² = 144 + 256 = 400
c² = (21)² = 441
a² + b² ≠ c²  (400 ≠ 441)
Therefore, a Triangle with side lengths of 12, 16 and 21 is NOT a Right Triangle
Note: Since a² + b² < c²  (400 < 441), the Triangle is an Obtuse Triangle