...squared exceeds the square of the third side by a right-angled parallelogram contained by the whole base and double that portion which lies between the perpendicular and the last-named third side’s subtending angle.

The 7th Chapter.

The description of the Geometrical Quadrant.

A large geometric diagram of a quadrant, featuring a curved scale marked with degrees (5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90) and a straight scale marked with numbers (3, 6, 9, 12). The center point is labeled 'A', the circumference point 'C', and the top right corner 'D'. There are two small sights at the top edge.

An ornamental drop cap 'F' featuring two figures holding a shield.

First, you must make a common, simple, large quadrant thus: with your compass, draw an arc or circumference that may be more, or at least sufficient, for a quadrant; then put both the feet of your compass on that arc, making two pricks. Now, the distance of these two points, divided into two equal parts and adding one portion to the aforementioned circumference or distance, shows a precise quadrant. You ought then to draw a line from the center to the outermost points of each side, which are the extremes of your quadrant. Again, draw a line from your center A to the middle of the quadrant's circumference C. If you wish, you may divide that quadrant into 90 degrees thus: first in 3 parts, then every third into 3, so you have 9 portions. Now, divide each of them in 2, which rises to 18. Then, divide each in 5 equal parts, which makes 90 degrees.