Transmuting circle portions; the equilateral triangle
Multiplying a quantity's equal parts while keeping their figure; a hexagon inscribed in a circle
This densely written sheet develops a method for dividing a portion of a circle into any number of equal similar portions and 'transmuting' that number into any other, using five ordered rules and figures of squares divided into parallels. Leonardo works numerically (6 x 4 = 24, 6 x 14 = 84) and geometrically, building an equilateral triangle whose side is the semidiameter of a circle and enters six times in its circumference. Diagrams at the right include a hexagon inscribed in a circle and squares partitioned into rectangles. The reasoning links the arithmetic of equal parts to the construction of the hexagon and its 'six greatest portions'.
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6 times 4 makes 24; 6 times 14 makes 84
Leonardo multiplies to count the portions of a circle: six times four gives 24 portions for the six greatest portions of the first figure, and six times fourteen gives 84. He thereby 'transmutes' the 6 portions of the first figure into 84 portions similar and equal to those of the fourth.
Transmutation of a number of portions into any other
By the second, third and fourth rules a given number of equal portions may be changed into any other number desired, and the same rule serves across the variety of circles and any other plane figure. He notes one can even change an even number into an odd number.
As parts grow in number they shrink in figure
Of a given continuous quantity divided into equal parts, the parts diminish as much as they grow in number. A given portion of a circle may be multiplied or diminished into any number one wishes without changing its figure.
Constructing the equilateral triangle e f m and its circle
Having drawn the parallel d c in the square a b c d, make an equilateral triangle e f m with sides equal to a side of the square; then, opening the compass to one side, set a point on the lower angle m and strike the circle e f S, which receives in its circumference the six greatest portions and holds exactly 84.
Definition of the equilateral triangle a b c
Each of the triangle's three sides is the semidiameter of one same circle and enters six times into that circle's circumference, as the triangle a b c demonstrates in itself.
