# Casey's angle 2

- Author:
- Maurice OReilly

This applet shows Casey's angle using BOC = B'O'C'
13 points are shown here, 7 large and 6 small. Move the seven large ones as you will to explore Casey's angle.
How can you accurately describe what you observe?

**projection from a point**- as opposed to**parallel projection**. Here again, Casey's angle is shown to be**perspective invariant**: