It is convenient to remember that 5-12-13 is a Pythagorean triple.
Her ladder is 12 ft above the ground where it rests on the house.
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Using the Pythagorean theorem, you are given the hypotenuse as 13 ft and one leg as 5 ft. Then the other leg is
.. √(13^2 -5^2) = √(169 -25) = √144 = 12
