Find the curve of shortest length between points (R0, 0, Z0) and (R1, Φ1, Z1) on the conical surface r = z tanα, where (r, φ, z) are cylindrical coordinates and α, the opening (half) angle of the cone, is a constant. Recall that the increment of length ds in cylindrical coordinates is given by ds2 = dr2 + r 2 dφ2 + dz2