betha=betha0+A*cos(azi)+B*sin(azi)
I have the values of the A and B from the experiments of the helicopter but there is no data of betha0 (cone angle).
I may be wrong, but since it is a teetering rotor, is this betha0 (cone angle) the same as pre-cone angle?
Different rotary aerodynamicist will sometimes use different symbols.
Wayne Johnson and Gordon Leishman uses the following. Gareth Padfield is more detailed but appears to be in agreement with the following;
Beta ~ blade flap angle (positive upward).
Betap ~ precone angle.
Betao ~ coning angle.
Beta1c ~ longitudinal tip-path-plane tilt angle (positive forward)
Beta1s ~ lateral tip-path-plane tilt angle (positive toward retreating side)
I assume that (azi) stands for 'azimuth'.
Hope that this helps.
Dave