Upper panel: Equal redshift angular power spectrum for the lowest redshift bin of Euclid, using 13 equi-populated bins. We show the full calculation result from CLASS as a black solid line, and the Limber approximation result as a purple dashed line. The green dashed line corresponds to the recalibrated version of the flat-sky approximation. Lower panel: Relative error (in %) of each approximation from the full calculation result.