Induced Axial Loading in Tapered Roller Bearings?

Hello, I'm having trouble reconciling the induced axial loading in a TRB as a result of an applied radial loading. "Essentials of Bearing Concepts" provides a formula using the various contact angles, however bearing manufacturers (SKF, NSK, Timken) all use an equation where Fa=0.5/Y*Fr (the 0.5 value is substituted as 0.6, 0.47 depending on source), where Y is a given thrust factor.

Is there something else I'm missing here? The "SKF" equation is giving drastically different values than the textbook.