A local farmer wants to keep his sheep safe. He has one mile of fence, with which to surround the sheep. Luckily there is a very straight river which he can also use. Obviously the farmer wants to fence off as much land as possible, what shape will the fenced off area be and how large?

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The fenced of area will be a large semi-circle with the river forming the diameter of the circle. The area will be about 0.2 of a square mile (1 / 2 * pi).

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