[ª] , [©] , [^] , [¨]Quadrangle¨Quadrangle / Making by foot of perpendicular(GC World : Sample ,Typical examples of GC)
Let's move A, B, C, and D
(1)What shape will EFGH always be?
(2)What shape will EFGH be when ABCD is a rectangle?
(3)What shape of ABCD makes EFGH a rectangle?
(4)Let's think about these kinds of problems.

GC/Win


Forum of Geometric Constructor by Y.Iijima