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Hi Awrongo. The sum of the interior angles of a triangle are 180 degrees. That means the sum of the exterior angles is 3x360  180 = 900 degrees. If you subtract the 90 degree "straight" parts (2 per corner), then you have 900  [3 x 2 x 90] = 900  540 = 360 degrees. That's a full circle. So the curved area is π square kilometers. Thus the exclusion zone is 1 x (3+4+5) + π = 12 + π square kilometers. Cheers,
 


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