My sister, 5 years younger than me, got high school geometry with a set of overheads that were used by a different, older, teacher when I was a sophomore. My m

My sister, 5 years younger than me, got high school geometry with a set of overheads that were used by a different, older, teacher when I was a sophomore. My memory of those lessons was that Mrs White only did things on the overhead slides, with wax pencils. A PowerPoint would have been lively compared to euclidean geometry on overhead slides.