Determine whether a Triangle with side lengths of 12, 15 and 20 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 = 15, c = 20  (c cannot be less than a or b)
a² + b² = (12)² + (15)²
a² + b² = 144 + 225 = 369
c² = (20)² = 400
a² + b² ≠ c²  (369 ≠ 400)
Therefore, a Triangle with side lengths of 12, 15 and 20 is NOT a Right Triangle
Note: Since a² + b² < c²  (369 < 400), the Triangle is an Obtuse Triangle