Forecast of the constraints for the w₀w_aCDM cosmological model (adopting a flat geometry) using only the Euclid primary probes, as described in Sect. 8.1.1. The sampled parameter space also included the cosmological parameters (Ω_bh², Ω_ch², H₀, n_s, A_s, w₀ and w_a) and several nuisance parameters listed in Table 5. The grey dashed lines show the fiducial values of the parameters, that are also listed in Table 5. The posterior distributions were obtained using CLOE v2.0.2 and the sampler Nautilus, with 4000 live points and 16 neural networks. For the photometric probes, we used ℓ_max = 5000 for cosmic shear and ℓ_max = 3000 for photometric angular clustering, and galaxy-galaxy-lensing, while for the spectroscopic probe we used, k_max = 0.3 h Mpc⁻¹. We show the 2D-posterior distribution for the parameters w₀ and w_a in detail, citing the corresponding FoM obtained for each probe as well as for the combination of both.