Top panel: measurement (solid line) from the halo catalogues and the analytical prediction (dashed line) using linear perturbation theory as given in Eq. (13). Bottom panel: same for . The plot shows all triangular configurations, in which the minimum and maximum separations for a triangular side are 50 and 120 h⁻¹ Mpc, respectively. Light blue vertical band corresponds to triangular configurations where one leg of the triangle is fixed, r₁₂ ∈ (100, 105) h⁻¹ Mpc.