MathDB
ASU 124 All Soviet Union MO 1969 pentagon with equal sides

Source:

June 23, 2019
geometrypentagon

Problem Statement

Given a pentagon with all equal sides.
a) Prove that there exist such a point on the maximal diagonal, that every side is seen from it inside a right angle. (side ABAB is seen from the point CC inside an arbitrary angle that is greater or equal than ACB\angle ACB)
b) Prove that the circles constructed on its sides as on the diameters cannot cover the pentagon entirely.