∬ R d A
Find the value of the above integral over a region R enclosed by
∣ x − y ∣ + ∣ x + y ∣ = 2 0 1 7 .
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Since the obvious graphical solution was posted, here's a computational solution. Let's first start with the inequality ∣ x − y ∣ + ∣ x + y ∣ ≤ 2 0 1 7 . If x > y then we have x ≤ 2 2 0 1 7 . If x < y such that x + y > 0 , then we get y ≤ 2 2 0 1 7 . If x < y such that x + y < 0 , then we get x ≥ 2 − 2 0 1 7 . If y < x such that x + y < 0 , then we get y ≥ 2 − 2 0 1 7 . Using this we can construct the integral A = ∫ − 2 2 0 1 7 2 2 0 1 7 ∫ − 2 2 0 1 7 2 2 0 1 7 d x d y A = 4 ( 2 2 0 1 7 ) 2 = 2 0 1 7 2 = 4 0 6 8 2 8 9 .
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This problem basically asks for the area bounded by the graph of
∣ x + y ∣ + ∣ x − y ∣ = 2 0 1 7
which, graphically, is
a square centered at the origin with side length 2 0 1 7 . And thus, we can easily get its area, and that would be 2 0 1 7 2 = 4 0 6 8 2 8 9