Oswald in the doorway: the blog of the Oswald Innocence Campaign, by Ralph Cinque

As per Wikipedia,  in Mathematics, slope is calculated by finding the ratio of the "vertical change" to the "horizontal change" between any two distinct points on a line.

"M" is the letter used for slope, hence:

m = y2-y1
        x2-x1

The Greek letter delta is used to indicate change. So, we have:

Here is an example of delta on a graph. It shows that for every two increments of run, there are three increments of rise. 

The -1 refers to the fact that it doesn't go through the origin. The diagonal line goes through -1 on the y axis. 

It is just an example, but we can plug in what we are concerned with:

So, you can see that in order for a shot hitting Kennedy to travel on into Connally, Conally has to be on the same diagonal as the other two. Look what happens if it's off even a little.

 It misses. And that is what happens because the slope of the line is constant. The "delta" between JFK and Connally has to be the same as the "delta" between Supposed Oswald and JFK. But, they're not. The delta between Supposed Oswald and JFK is over 20 degrees. But, the delta between JFK and Connally is at most 7.96 degrees. So, Connally is definitely off the line from Supposed Oswald to JFK. 

And we can see it with our naked eyes just by looking through the scoped view.