The sixfold division of the circle proved by its bisangles
62 bisangles make a sixth; 124 portions times six give 744
Continuing from the recto, Leonardo argues that the sixth part of the circle contains 62 bisangles, which halved give 124 portions; multiplied by the six sectors of the circle these yield 744 portions, verified by dividing 744 back by six to recover 124. He explains why six is the natural divisor of every circle: the chord of a sixth-arc enters the circumference six times and the diameter twice. A hexagon inscribed in a circle and a hexagon filled with six segments are drawn at the upper left, with columns of multiplication confirming the counts. He adds that the ways of dividing a circle's portions are infinite.
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62 bisangles compose the sixth part of the greatest circle
From the sixth part of the surface Leonardo draws out 62 bisangles, or equivalently 124 half-portions; multiplied by the six sectors these make 744 portions of the whole circle. The proof is to divide 744 by 6 and recover 124, the count that joined together equals the greatest portion a-b of the greatest circle.
Why six divides every circle
Six is the divisor of all the portion-numbers that any circle can hold, because the chord of the arc of a sixth part enters six times into the circumference and twice into the diameter, and the arc itself enters six times into the circumference. Leonardo notes this property belongs to no other kind of portion.
124 portions multiplied by six give 744
The right margin repeats the operation: multiply the 2 bisangles of the sixth part by 2 to make 124 portions, then multiply those 124 by the six sectors of the circle. Multiply 124 by 6 to get 744, and divide 744 by 6 to return to 124.
Hexagon inscribed in a circle and its six segments
The left margin captions two figures at the upper left: a hexagon inscribed in a circle and a hexagon holding six bisangles. The label a marks how one is an aliquot part of the six into which the whole circle is divided, that is, the portion a into which the circle is divided.