9514 1404 393
Answer:
x = √70
Step-by-step explanation:
The right triangles are all similar, so we can write the ratio of long side to hypotenuse as ...
x/(7+3) = 7/x
x^2 = 7(10) = 70
x = √70
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Additional comments
This is called a "geometric mean", where x is the square root of the product of two numbers, 7 and 10. Those happen to be the lengths of the adjacent segment of the hypotenuse and the whole hypotenuse.
The same relation holds for BC:
BC = √(CD·CA)
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A slightly different geometric mean relation holds for the altitude BD:
BD = √(DC·DA)
