It is clear that both lines are double the length of the original line ED, that LH has its centre at E, and that HK has its centre at D. Note, additionally, that EH (which is equal to CD) carries the common measure (or unit) N an exact number of times, as does EC and, by extension, CH. It remains then to prove that A applied at E, and B applied at D, will have their centre of gravity at C.