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MathNet 2013 Question 70

Math Olympiad Vault · MathNet 2013

Question 70

We call a convex pentagon in the Euclidean plane "special" if either all of its sides are of equal length or all of its interior angles are equal. We call it "very special" if either all of its sides are of equal length and two of its interior angles equal or if all of its interior angles are equal and two of its sides of equal length. Prove that every very special pentagon must have an axis of symmetry.