Unrolling the cone and squaring the circle
A cone's surface developed as a triangle; a semicircle folded into a cone; the largest cylinder in a cube
Leonardo continues his cone constructions across two labelled figures. In the 'second' figure (a d, b n c m e) the complete revolution of the base together with the surface of a cone whose axis equals its base diameter leaves upon a plane a trace equal to the cone's surface, an equilateral triangle c d. In the 'first' figure (a b v c d; f g h e K i) a semicircle whose curved ends are brought into contact folds into a cone whose base circle is half its surface. Doubling this composes the quadrature of the whole circle and a cylinder whose rolled trace equals four times the base circle, twice the cone's surface, and the surface of a sphere containing four such circles, declared the largest cylinder drawn from a cube.
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Cone with axis equal to base diameter unrolls as triangle c d
The complete revolution of the base with the surface of the cone whose axis equals its base diameter leaves, on a flat place, a trace equal to the cone's surface, which is an equilateral triangle c d.
Semicircle folded into a cone; the quadrature and largest cylinder
Bringing the ends of a semicircle's curved side into contact forms a cone whose base is a circle half that cone's surface. Doubled, it composes the quadrature of the whole circle and a cylinder whose rolled trace is four times the base circle, twice the cone's surface, and equal to a sphere holding four such circles, said to be the largest cylinder from the cube.