One of the diagonals of the parallelogram with sides 4 and 7 is 9. Find the second diagonal.

univerkov | July 30, 2021 | education

To solve the problem, we will use one of the properties of the parallelogram diagonals:
d1² + d2² = 2 * (a² + b²).
We express and find from this formula one of the diagonals:
d2² = 2 * (a² + b²) – d1² = 2 * (16 + 49) – 81 = 130 – 81 = 49;
d2 = √49 = 7.
Answer: The second diagonal of the parallelogram is 7.

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