This should have been explained to you . . . at some time, by someone.
I know that the formula is : .
But what if one of the direction numbers is zero?
Do you just drop that part of the equation since it is undefined? .No
Suppose the direction contains a zero: .
Believe it or not, we are allowed to write this:
. . . . .
The standard "excuse" is that those denominators are simply "holders"
. . for the components of the direction vector.
So that we are not really dividing by zero,
. . we're just "storing" the zero there. . . LOL!