[Yoda]

Yoda, aren't the arc of approach, angle of approach and plane line on one and the same plane? It would seem to me to be the case so the right forearm to trace these at the same time.

More precisely, the two Visual Equivalents (of the Geometric Plane Line) -- the Arc and Angle of Approach -- are the illusions that appear to the player to be on the ground. It is the Arc and Angle of Attack that are on the Inclined Plane itself.

When you use the 'on the ground' Angle of Approach as the Delivery Line, you abandon the original Plane Angle (with its Geometric Plane Line) and substitute a steeper one erected on the Angle of Approach. The Right Forearm then traces the new 'Inside-Out' Baseline, and the Sweetspot covers it.