(I.29) Proposition 29, 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 29, we prove that if two parallel lines are intersected by a third line, then the alternate interior angles, are congruent, the exterior angle is congruent to the opposite interior angle, and the sum of two interior angles on the same side are congruent to the sum of two right angles. Playlist of Euclid's Elements in link below: http://www.youtube.com/playlist?list=PLFC65BA76F7142E9D