Answer:
6√2 ≈ 8.485 inches
Explanation:
The radii and the chord together make an isosceles right triangle with legs 6 inches long. The hypotenuse of such a triangle is √2 times the leg length. So, the chord will be 6√2 in long.
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Comment on isosceles right triangle
It is worth remembering that the hypotenuse of an isosceles right triangle is √2 times the leg length. This is easily found using the Pythagorean theorem:
... c² = a² + b²
... c² = 1² + 1² = 2 . . . . for legs of length 1
... c = √2 . . . . . . . . . . take the square root.
Scale this result as needed for any particular problem. Here, the scale factor is 6 inches.