Difference between two circular portions
A square inscribed in a circle set over a semicircle, comparing portions o and n.
A small figure of a square inscribed in a circle set over a semicircle heads this short note, which asks what difference lies between two circular portions o and n. Leonardo answers that removing p from p o leaves the difference p, which equals portion S, and that the portion is double portion a. He reasons that o equals portion a together with its companion t, so that a o g equals g o p.
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Comparing portions o and n by subtraction
To find the difference between portions o and n, take p from p o: the remainder p is the difference sought, equal to portion S, while the portion is double portion a. It follows that o equals portion a with its companion t, so that a o g equals g o p.