Definitions of double and subdouble ratio
'Dupla' and 'subdupla'; a square inscribed within a square
A short note on a small fragment defines two proportional relations: a quantity is 'double' (dupla) when it contains another quantity twice, and 'subdouble' (subdupla) when it goes twice into another. The examples given are 2 compared to 1 (double) and 1 compared to 2 (subdouble). Beneath the text a small geometric figure shows a square with a second square inscribed within it and its diagonals drawn, illustrating the halving and doubling of area.
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Double and subdouble quantities defined
A double quantity is one that contains another compared to it twice over; a subdouble is one that enters twice into the quantity compared to it. Thus 2 compared to 1 is called double, and 1 compared to 2 is called subdouble.
Square inscribed within a square
Below the note a small figure shows a square with a second square inscribed within it, corner to mid-side, together with the diagonals. The inner square is half the area of the outer, giving a visual image of the double-and-half relation defined in the text.