9514 1404 393
Answer:
40 ft, 41 ft
Explanation:
The Pythagorean theorem tells you the relation between the sides and hypotenuse is ...
9² +x² = (x +1)²
81 +x² = x² +2x +1
80 = 2x
40 = x
The lengths of the missing sides are 40 feet and 41 feet.
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Additional comment
For each odd number at least 3, there exists a right triangle with sides that differ by 1. As here, the length of the other leg is (n²-1)/2 for odd length side n.