I used this Which One Doesn’t Belong? to start our unit on angles and triangles. I love how starting with something like this gives me insight on where students are at with this topic based on their answers and the vocabulary they are using.
After taking some notes on different vocab words we came back to the same image at the end of the day, and I asked students to use the new vocabulary to describe the images.
I also had students do this Desmos Polygraph several times throughout the unit as they learned new vocab words.
Sum of Angles of a Triangle
In one of my classes, I had students cut out a triangle, rip off the angles, and put those pieces together to form a line. It didn’t go quite as I hoped with that class, so in the other classes I was the only one who cut the triangle. I would like to figure out a way so that more students see what I want them to see as they’re cutting the triangles and putting the angles together.
Jo Morgan shared several good Angle Chase activities in this Math Gems post.
Interior Angles of Polygons
After talking about the sum of the angles in a triangle, I have students Notice/Wonder with polygons divided into triangles for them to figure out the sum of the interior angles of polygons.
After they’d done some practice with that we made a table to come up with the general formula.