And since the greater
piece of a (straight-line) subtending two sides of a pen-
tagon, such as AC, (which is) cut in extreme and mean
ratio is equal to the side of the pentagon [Prop. 13.8]—
that is to say, to DC—-and the square on the greater piece
added to half of the whole is five times the (square) on
half of the whole [Prop. 13.1], and CM (is) half of the
whole, AC, thus the (square) on DCM, (taken) as one,
is five times the (square) on CM.