This proposition depends so thoroughly on Definition 10 that I’ve made the contents of the definition the theme for the artwork. Definition 10? Gives the meaning of right angle and perpendicular. (That’s definition 10 in greek at the top of the piece.) Proposition 11 gives the procedure for drawing one line at right angles to another line. And definition 10 is an essential piece of the proof because it states that adjacent equal angles are right angles.
The notes to definition 10 triggered the plumb line imagery. Heath’s notes remind the reader that in ancient times the perpendicular to the earth was a gnomon, or upright stick. In more modern times, the perpendicular to the earth is a plumb line. That got me thinking about using a plumb bob and its accompanying string in the imagery for the artwork, which you can see, I milked more than a little bit. There’s some great vintage imagery relating to plumb bobs. One image, an ad for the Seaboard Coast Line Railway, printed the phrase “straight as a plumb line.” This ad is so wonderfully nostalgic that I had to put that phrase into the piece.