Kushpel, Alexander2026-04-032026-04-0320211303-61491300-0098https://hdl.handle.net/20.500.12416/16059https://doi.org/10.3906/mat-1910-111We give the solution of a classical problem of Approximation Theory on sharp asymptotic of the Lebesgue constants or norms of the Fourier-Laplace projections on the real projective spaces P-d (R). In particular, these results extend sharp asymptotic found by Fejer [2] in the case of S-1 in 1910 and by Gronwall [4] in 1914 in the case of S-2. The case of spheres, S-d, complex and quaternionic projective spaces, P-d(C), P-d(H) and the Cayley elliptic plane P-16 (Cay) was considered by Kushpel [8].eninfo:eu-repo/semantics/openAccessFourier-Laplace ProjectionJacoby PolynomialLebesgue ConstantArticle10.3906/mat-1910-1112-s2.0-85103726765