Which classification best represents a triangle with side lengths 6 cm, 10 cm, and 12 cm?

The triangle is valid because 6 + 10 > 12. To classify its angles, compare the square of the longest side with the sum of the squares of the other two sides: 12² = 144, while 6² + 10² = 36 + 100 = 136. Since 144 > 136, the triangle is obtuse, so the correct choice is “obtuse, because 6² + 10² < 12².”

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