Definition:Perpendicular Distance

Definition
Let $\mathcal L$ be a straight line.

Let $P$ be a point not on $\mathcal L$.

Let a perpendicular be dropped from $P$ to $\mathcal L$, intersecting $\mathcal L$ at $A$.

The perpendicular distance from $P$ to $\mathcal L$ is defined as being the length of the line $AP$.


 * Perpendicular-Distance.png

Also see

 * Perpendicular through Given Point
 * Perpendicular is Shortest Straight Line from Point to Straight Line