Question

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Answer 1

One more thing: the big triangle is a right triangle because the two directions North, East are perpendicular.

Now imagine that you can go straight from the city til you hit the hypotenuse at a right angle. How long is this distance? If this turns out to be less than 36 then at least we know that there is a period during which there is signal.

Answer 2

I don't know what to do next. Maybe something like 40^2 + 45^2 = h^2 and then 40^2 - 36^2 = a^2; 45^2 - 36^2 = b^2; and a + b = h = sqrt[40^2 + 45^2]???