Answer:
8√2 ≈ 11.31 meters
Explanation:
The straight-line distance is the hypotenuse of an isosceles right triangle with legs 8 meters. So, the distance is 8√2 meters, about 11.31 meters.
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Of course, you know that a right triangle with legs 1 and 1 has a hypotenuse of ...
√(1² +1²) = √2 . . . . . given by the Pythagorean theorem
Scaling this by a factor of 8 meters gives you legs of 8 meters and a hypotenuse of 8√2 meters.