GoGeometry Action 186!

Creation of this resource was inspired by this problem posed by Antonio Gutierrez (GoGeometry). You can move any of the LARGE POINTS anywhere you'd like AT ANY TIME. The bottom left slider controls the size of the colored angle. How can we formally prove the phenomenon dynamically illustrated here? Is it possible to make the longest perpendicular segment different from what is originally shown? Try to move the points and/or bottom left slider to make this happen. How would you describe what you see now?

Quick (Silent) Demo