I cracked myself up today

I was looking through my lesson on slope from last year, and there were a bunch of frames with this skateboarding guy to help show how to think about slope.

So I'm flipping through the frames and I come to one where I was trying to explain how the slope of a vertical line is undefined, which I completely had forgotten about...

 

I laughed pretty hard.  Chalk up a positive for having a terrible memory.

(Now with 100% less titlefail!)