Perpendicular Distance Along a Normal

Perpendicular Distance Along a Normal

## Formula

For a point $$P(x_1,y_1)$$ and line:

$$Ax+By+C=0$$

the signed perpendicular distance is:

$$d_s=\frac{Ax_1+By_1+C}{\sqrt{A^2+B^2}}$$

## Usage

- Used when the sign of the distance is important, such as in determining the side of a line on which a point lies.