Circle and square: doubling, portions and proportion
Inscribed and circumscribed circles and squares, rosette grids and area arithmetic
A dense geometry sheet exploring the doubling relations between circles and squares. Leonardo states that the circle through a square's four corners is double the circle touching its four sides, and dually for the squares, and that circle is to circle as square to square by squaring the diameter. He also divides the greatest circle into 232 minimal portions and reasons about the 116 that remain, with supporting multiplications such as 12 by 7 and 15 by 6. Interlocking-circle rosettes and interlace knots crowd the sheet, and a later hand has added an untranscribed caption.
On this page
The circle of the corners is double the circle of the sides
The circle that touches the four corners of a square is double the circle that touches its four sides; and dually, the square whose four sides touch a circle is double the square whose four corners touch that same circle.
232 portions of the greatest circle
Halving the greatest portion of the greatest circle and halving its 232 smallest portions leaves 116 as voids, the value of 116 minimal portions. The greatest circle is to have its circumference reduced by 6 portions together with the reduction of the 116.
Circle to circle as square to square
The proportion from circle to circle is as that from square to square, obtained by multiplying the diameter by itself. It reduces the ratio of the circles to the square of their diameters.
Two circles tangent to one square are double
Of two circles tangent to one square, the outer touching its four corners and the inner touching the middle of its four sides, the one is without doubt double the other.
Multiplications and doublings
Worked figures support the geometry: 12 times 7 makes 84, 15 times 6 makes 90, and 116 doubled makes 232. The columns tie the areas and portions to concrete numbers.
Rosette grids and interlace knots
Clusters of overlapping circles form hexagonal rosette (flower-of-life) grids at the top and lower centre, and small woven interlace knots are threaded among them.
