Perpendiculars

The basics of the perpendicular tool are as follows. The Perpendicula tool creates a perpedicular line to an existing line using the following steps:

1. Select an existing line.
   
2. Select the point on the existing line where the perpendicular line will start. You can select a point past the endpoints.
   
3. Select a third point to set the length of the perpendicular line, or enter the length in the Inspector Bar.
   

But what you may not know is that the perpendicular tool also creates perpendicular lines to other entity types as well. These entities include: Circles, Circular Arcs, Ellipses, Elliptical Arcs, Splines, Beziers.

All of the red lines below were drawn using the Perpendicular tool. An important point to understand is that the perpendicular line is perpendicular to the tangent of the curve at that point on the curve. This means you can use the perpendicular tool to generate tangents to all of these curves just by using the Perpendicular tool twice, first to the curve, and then to the new perpendicular line.