Geometry of rectangles and squares with computed areas
A 12-unit base yields a 6-high rectangle of area 72 and a square of area 144
The leaf works through rectangles and squares treated as areas. One figure sets a square of side 8 beside a strip of 4 and is captioned 'known'; another builds on a base of 12 (vertices a, b, c) a rectangle 6 units high whose area is given as 72, and a square of side 12 whose area is 144, closed by the note 'conclusion of the proposition'. The numerals and the letter b here were written in the ordinary, non-mirrored sense. Faint mirror-script also appears at the foot of the page.
On this page
Rectangle on base 12 with area 72
On a base labelled 12 (endpoints a and c) a rectangle 6 units high is drawn, its far corner b marked, and its area entered as 72 — that is, 12 times 6. The number 6 and the letter b were written the ordinary way round rather than mirrored.
Square of side 12, area 144
A square standing over a rectangle has its top and bottom sides marked 12 and its area given as 144 (12 squared). The figure is closed with the caption 'conclusion of the proposition'.
Square of 8 with a strip of 4, 'known'
An upper figure places a square whose side is 8 next to a narrow strip marked 4, captioned 'known'. It fixes the givens for the area work that follows.