Multiplying lines to form rectangles
Two lines a and b joined at a right angle generate their rectangle
The page treats multiplication as a geometric operation on lines. Two lines a and b are joined at a right angle so that together they enclose a rectangle, and Leonardo notes that the multiplication of lines without name makes the rectangle of the two of them. Further figures show pairs of lines meeting at right angles, a horizontal line divided into five parts against a vertical line, and rectangles divided into five parts labelled b.
On this page
Rectangle as the product of two lines
Lines a and b are set at a right angle and closed into a rectangle. Leonardo writes that the multiplication of lines without name makes the rectangle of the two of them, treating the enclosed area as the geometric product of the two sides.
Lines a and b enclosing a right angle
Two given lines a and b are first drawn separately and then joined so as to enclose a right angle. This right-angled pairing is the step that lets their lengths be multiplied into an area.
Line and rectangle divided into five parts
A horizontal line labelled b is divided into five parts against a vertical line a, and a rectangle built on it is likewise cut into five strips. The subdivision prepares the multiplication of the divided line by the other side.