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MathNet 1969 — Part 01 Question 10

Math Olympiad Vault · MathNet 1969 — Part 01

Question 10

Given a pentagon with equal sides.

(a) Prove that there is a point $X$ on the longest diagonal such that every side subtends an angle at most $90$ degrees at $X$.

(b) Prove that the five circles with diameter one of the pentagon's sides do not cover the pentagon.