As we are working through my favorite unit of the year, relations and functions, I'm loving the opportunity to pull out my shower curtain coordinate plane. I blogged about creating this coordinate plane using electric tape, duct tape, and a shower curtain from Dollar Tree here.
A few years ago, I made a promise to myself to let my students discover the vertical line test for themselves. To aid my students in thinking about the what functions look like, I asked my class for a few volunteers.
First, I asked my students to stand on the coordinate plane so that their bodies formed a function.
Next, I asked them to stand on the coordinate in such a way that they were NOT a function.
After repeating this process several times, I asked them what they noticed. It became pretty clear to them that the points in the non-functions always lied in vertical lines.