A horizontal line has a slope of zero.

A vertical line has no slope.

Some students have difficulty with the idea that no slope and a slope of zero can mean two different things.

"Isn't zero the same as none?" they ask.

Not always. I used to explain the difference between none and zero like this.

Before the football season begins, the Cleveland Browns have no record. They've played no games; they have no record.

"After they lose the first game," I'd say, "their record is 0."

In those days it was funny.

The Browns would lose some, they'd win some, and me talking about them opening the season with a loss was just an illustrative point.

This year the Browns ended the season with a record of 0.

They lost all sixteen games that they played.

They've been bad for a long time - but this was bad. Their record at the end of the season was 0.

In the days when the Browns would win and even go to the playoffs it was fun to have rivalries. It was fun to trade insults with fans of other teams. Now they don't feel right making fun of the Browns. It doesn't seem fair.

There was a time when I hated our arch-rivals the Steelers. But in the past few years I've actually rooted for the Steelers to win in the playoffs.

This year was different.

I just didn't care.

I had no dog in this fight.

This isn't about geometry or football, but this past weekend I watched four football games that were all a lot of fun for different reasons.

Towards the end of the first game I noticed that I didn't care who won and I was enjoying the games a lot more than I expected.

In a way it was like old times. My brother and sister and I were visiting my parents and we all watched the end of the game together.

When you don't care what happens, the point isn't the outcome - it's the game itself. It seemed to me that the officials missed some calls in the final two minutes that effected the outcome of the game and I didn't care. The game was a lot of fun and I didn't care if Philadelphia or Atlanta won. The game came down to the final seconds and was exciting to watch.

Maggie and I drove back from Oberlin and got home mid-way through the second quarter of the second game.

I used to hate New England.

Before that I used to love them. The year after college, my roommate and I drove down for a couple games.

But then I hated them.

Not because they were seen as cheaters but because they were so good. I'm not proud of that fact - but I think that's the reason.

As I watched them Saturday, I didn't care.

I didn't care if they won or loss. This was probably a good thing because it was clear pretty early that they were going to win. I just enjoyed watching them move the ball. It was a clinic in a rich assortment of play calls and adjustments made at the line. In the end, I didn't even mind that the Patriots won.

By the time I turned on the first game on Sunday, the Pittsburgh Steelers were already down 14 - 0 to the Jacksonville Jaguars.

I didn't care.

I was surprised to see that I had no pleasure in seeing them down.

By the end of the game, the Steelers had scored 42 points and lost. If you didn't care about the outcome, it was a tremendously fun game. If you were a Steelers fan you probably replayed every blown play and missed opportunity in a game of "what if".

The final play of the final game is the one that leads the highlight reel of the weekend's games.

The New Orleans Saints were up by a point with ten seconds left on the clock.

It's hard to know what the best strategy is. The Vikings lined up on their own 39 yard line. I guess you try for a twenty -five yard play to get within field goal range and kick a field goal.

Nope.

Sure Stefon Diggs caught the ball on the 34 yard line and could have stepped out of bounds at the 30 for a thirty-one yard gain and field goal attempt. But somehow he spun around and ran for the end zone. Had he been tackled, his team would have lost by a point. Instead he ran it in and they won by five.

I kind of wanted Minnesota to win but I didn't really care. I couldn't have even told you the name of the quarterback before the game.

So if this isn't about geometry or about football, what is it about?

I've been reading books about meditation and mindfulness lately.

Don't roll your eyes.

I'm just saying that my experience watching the games was different when I didn't care about the outcome.

Despite what we think as fans, there's nothing we can do to change the outcome of a game.

I'm not saying we shouldn't support teams and get involved and enjoy games because we care - I'm just saying that now and then, in games or life, we should just enjoy what's around us without an agenda.