An interactive applet and associated web page that demonstrate how to find the perpendicular distance between a point and a line that is either vertical or horizontal, given the coordinates of the point and the equation of the line. The user can set the orientation of the line and position, along with the location of the point. As the line is altered or the point dragged, the distance is recalculated.

The grid and coordinates can be turned on and off. The distance calculation can be turned off to permit class exercises and then turned back on the verify the answers. The applet can be printed as it appears on the screen to make handouts.

The web page has a full description of the concept of the concepts, a worked example and has links to other pages relating to coordinate geometry.

Applet can be enlarged to full screen size for use with a classroom projector. After use in the classroom, student can access it again from any web browser at home or in the library with no login required.

This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.