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Answer:
We can use the Pythagorean theorem to show that both triangles contain equivalent shorter legs:
Triangle A:
13² = 12² + b²
169 = 144 + b²
25 = b²
b, or the other leg, = 5 cm.
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Triangle B:
c² = 12² + 5²
c² = 144 + 25
c² = 169
c = 13 cm.
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Both triangles contain legs with side-lengths 5, 12, and 13 cm. The triangles are congruent because the lengths of the corresponding sides between triangle A and B are equivalent, which was proved using the Pythagorean Theorem.