 Solution

ID: past-exam-of-the-options-ii-course-of-the-university-of-oxford/2008/e/e3/b/solution

The condition

max (∣ x - 1/2∣, ∣ y ∣) \leq 1/2

gives the closed square

[0, 1] \times [- 1/2, 1/2] .

Its four edges and corners are included, as shown in the left panel of the figure below.

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