MathDB
Board

Source: RMO 2003, District Round

April 22, 2006
vectoranalytic geometryfunction

Problem Statement

On a board are drawn the points A,B,C,DA,B,C,D. Yetti constructs the points A,B,C,DA^\prime,B^\prime,C^\prime,D^\prime in the following way: AA^\prime is the symmetric of AA with respect to BB, BB^\prime is the symmetric of BB wrt CC, CC^\prime is the symmetric of CC wrt DD and DD^\prime is the symmetric of DD wrt AA. Suppose that Armpist erases the points A,B,C,DA,B,C,D. Can Yetti rebuild them? \star \, \, \star \, \, \star Note. Any similarity to real persons is purely accidental.