Cutting Any Part from a Triangle with One Compass Setting
A third, a quarter, or any part at will
A subdivided triangle shows how, in Leonardo's words, 'with a single opening of the compass' one can give 'a third or a quarter or whatever part I wish.' The numbers 3 and 6 accompany the figure, whose internal parallels mark off the proportional parts. The sheet also bears further faint fractions written around the drawing. The pencil work is light.
On this page
One compass opening for any part
The note explains that with a single setting of the compass one may cut off a third, a quarter, or any desired part of the figure. The subdivided triangle carries the measures 3 and 6 to demonstrate the method.
Fractional parts of the figure
Around the triangle further fractions are jotted, dividing the figure into successive parts. These express the aliquot parts, a third, a quarter and so on, that the construction is meant to produce.