(I.14) Proposition 14, Euclid's Elements

Support my channel with this special custom merch! https://www.etsy.com/listing/994053982/wooden-platonic-solids-geometry-set Learn this proposition with interactive step-by-step here: coming soon In proposition 14, we prove that if a straight line has two lines drawn outward from the same endpoint making the adjacent angles congruent to the sum of two right angles, then the two lines must be in a straight line with each other. Playlist of Euclid's Elements in link below: http://www.youtube.com/playlist?list=PLFC65BA76F7142E9D