On Gnomons

J._M. Aarts, R._J. Fokkink

A gnomon is a shape which, when added to a figure, yields a figure that is similar to the original one. Gazalé~[4] conjectured that if the gnomon is a regular polygon and the figure to which it is added is a finite polygon then the gnomon is a triangle or a square. We prove this conjecture to be correct.