🚀 go-pugleaf

gm115@emu.pmms.cam.ac.uk (Gabor Megyesi) writes:
>The answer is yes. It is a general theorem that anything you can do with a
>ruler and compass you can also do with a compass alone, I wish I remembered
>who proved it. Of course you cannot draw a straight line with a compass,
>but we consider a straight line to be known if there are two known points

The sufficiency of the compass was shown by Mascheroni in 1797 (although it was
apparently proved 125 years earlier by Georg Mohr), and its dual, that every
construction that can be done with compass and straight edge can be done with
straight edge alone, provided that one circle and its center are given, was
proved in 1833 by Steiner (and similarly, a circle is considered to be known
if we have its center and radius).

-- 
 -- Erick, the smallest number expressible as the sum of two distinct triangle
           numbers in two distinct ways.