In geometry today, I was trying to get my kids to understand why if two lines have opposite reciprocal slopes, they must be perpendicular.
It’s actually a pretty deep idea — at least to me it is. I created something I thought would help them think carefully about it.
It actually harks back to the paper folding problem we started the year with.
This was a really tough thing for kids to figure out. But with a little guidance, each group was getting closer and closer to figuring out some reasoning for why opposite reciprocal slopes yields perpendicular lines. One group finished figuring it out, and this one kid in that group had the key insight.
He left saying to me, “I feel smart.”
one good thing 