What To Do When You Forget Your Lines

Greetings, Mr. Carter

Sometimes being honest can have its downsides. My son, Tad, asked me if I could help him remember what the name of a line's slope is if it goes straight up and down, and what it's called if the line goes straight from left to right without going up and down at all.

I remember one of them is a 0-slope, and the other one is called no slope, but I had to confess to him that I did not know which is which. 

Can you help me, so that I can tell him? He has a quiz this Thursday. 

Mathematically, 

A. Lincoln


Hello, Mr. Carter

I cannot tell a lie. I also struggle with this.

Respectfully, 

G. Washington

I understand the struggle, fellows.

Luckily, just a couple years ago, I ran across a very handy way to tell these apart.

First off, you can remember that a 0-slope always is a horizontal line, or from side to side, but using this visual reminder:

Then the up-and-down slope is often called "undefined," although for many years I knew it as "no slope". Luckily this one works either way:

I'll go into how to name these lines on a coordinate plane tomorrow, but for now, I think you'd have to admit that it's easier to remember than you thought!

I hope you gentlemen have a fantastic Presidents' Day, and that everyone comes back soon for more mathematical fun at Mr. Carter's Dojo.