Polygon remains non-rigid
Source: Kvant Magazine No. 6 2020 M2608
March 9, 2023
geometrypolygonKvant
Problem Statement
A hinged convex quadrilateral was made of four slats. Then, two points on its opposite sides were connected with another slat, but the structure remained non-rigid. Does it follow from this that this quadrilateral is a parallelogram?Proposed by A. Zaslavsky[img width="40"]https://i.ibb.co/dgqSvLQ/Screenshot-2023-03-09-231327.png