Inverse functions discovery— here’s a simple, hands-on idea for introducing inverse functions. It can also be used to discover geometric transformations over y = x. All you need is a square coordinate grid, a hole punch and a pencil or pen. Recording all class data on the whiteboard as a class may be fun to do, too. Students will start to see that x and y swap spots in inverses. The hole punch I’m using here is 1/8th-inch with a 2-inch reach. #inversefunctions #geometrictransformations #teaching