Hi, first post and 30+ years since my last math class.

I am trying to construct a tapered helix that is constrained to a specific included angle. I have the equations for a tapered helix given height, pitch, radii, but cannot get my head around how to force the helix to grow within a given included angle.

X(t) = ( R1 + (t*(R2-R1) / (2*T*PI)) )*COS(t)
Y(t) = q*( R1 + (t*(R2-R1)) / (2*T*PI) )*SIN(t)
Z(t) = (H*t)/(2*T*PI)

R1 = big radius
R2 = small radius
T = number of turns (f(pitch,height))
H = height
q = handedness

Google tells me a lot about antennae and DNA, but not much about this. Any help appreciated.