x coordinate as a function of q_x for Q1D-3SIN (top panels) and ANI-3SIN (bottom panels) initial conditions at various output times, with Δ = 0.005 (left), 0.01 (centre), and Δ_sim = a_sim/a_sc − 1, as given in the right column of Table 1 (right). The solid and dashed curves correspond to q_y = 0 and , where is the maximum extension of the caustic in Lagrangian space along the q_y-axis, while q_z = 0. We present the results predicted by the pure 15LPT solution (black) and its Taylor expansion expression in the Lagrangian coordinate up to up to 𝒪(q³) (orange) and up to 𝒪(q⁵) (blue).