A triangle has side lengths of 18cm, 80 cm, and 81 cm. Classify is acute, obtuse, or right.
3 Answers
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Put the two smaller sides into the Pythagorean Theorem to see what length the hypotenuse would be if it were a right triangle. (I get 82 cm.) Since the third side is only 81 cm, that means the angle across from it isn't quite oƿє-ṅєd up to 90 degrees. (Smaller sides mean smaller angles across from them.) The triangle is acute.
If the third side was greater than 82, the triangle would be obtuse.
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18^2 + 80^2 = 6724
81^2 = 6561
18^2 + 80^2 > 81^2
obtuse triangle
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acute
