MathDB
TOT 239 1989 Autumn A S3 area of cross wanted, rotate _|_lines, circle

Source:

March 12, 2021
geometryarea

Problem Statement

Choose a point AA inside a circle of radius RR. Construct a pair of perpendicular lines through AA. Then rotate these lines through the same angle VV about AA. The figure formed inside the circle, as the lines move from their initial to their final position, is in the form of a cross with its centre at AA. Find the area of this cross.
(Problem from Latvia)