If VAPA1 = (Tan PA1) - (Arc PA1) = INVPA1

The AGMA "Manual of Gear Design" book descibes this as a "vectorial angle".

The book gives an example:

VAPA1 = (Tan 14.5°) - ((PI/180) * 14.5°) = .00554

INVPA1 = .00554

If I have INVPA2 = .057897

I need to find PA2

Suggestions?

FlabbyRoach