It's important to know that the converse of the Pythagorean Theorem states that if the square of the length of the longest side of a triangle is equal to the sum of the squares of the other two sides, then the triangle is a right triangle.
Let's apply the converse to the given triangle.
As you can observe, this result is false because 36 is not equal to 36.
Therefore, by the converse of the Pythagorean Theorem, the triangle is not a right triangle.