Sketch of the proposed conical model for the jet. a. View of the jet in projection onto the plane of the sky. We indicate the apparent opening angle with θ′. b. Projection of the jet onto the x, z plane. Here θ is the true opening angle and ϕ the inclination angle of the jet axis with respect to the plane of the sky. The observer lies at z = −∞. The z′ axis coincides with the axis of the cone, while we choose y′ = y.