We know that a vertical line will always have a null run value
Then run = 0 always
We know that any number divided by 0
Z/0
isn't determinated because if we approximate to 0
Z/1 = Z
Z / 0.1 = 10Z
Z / 0.01 =100 Z
Z / 0.001 = 1000Z
Z / 0.0001 = 10000Z
and so on.
Then if we divide it by a number nearer to zero the answer will be higher and higher, so if Z is divided by zero the result is infinite
If we get approximate to zero by the negative
Z / -1 = -Z
Z / -0.1 = -10Z
Z / -0.01 = -100 Z
Z / -0.001 = -1000Z
Z / -0.0001 = -10000Z
Then if we divide it by a negative number nearer to zero the answer will be lower and lower, so if Z is divided by zero the result is -infinite (negative infinity)
Therefore, if a number is divided by zero it is like if the answer is positive infinity and negative infinity at the same time. So we say it is undefined