We are given a triangle ABC and three rectangles R1,R2,R3 with sides parallel to two fixed perpendicular directions and such that their union covers the sides AB,BC, and CA; i.e., each point on the perimeter of ABC is contained in or on at least one of the rectangles. Prove that all points inside the triangle are also covered by the union of R1,R2,R3. geometryrectangleperimeterLaTeXgeometry proposed