Marginalized 1D and 2D constraints on the parameters A, n_s, A_BAO, k_BAO, α, γ, and β from the Fisher matrix analysis, using a Euclid-/DESI-like survey. The 1D histograms show the posterior distributions, with titles indicating the median and 68% confidence intervals in scientific notation. The 2D plots show contours from samples and overlaid Gaussian ellipses (red solid for 68% and dashed for 95% confidence regions). Fiducial values are marked with lines.