The standard technique to solve partial differential equations used Fourier series but Cauchy, Abel and Dirichlet had all pointed out problems associated with the convergence of the Fourier series of an arbitrary function.
Ang standard na pamamaraan upang malutas ang mga bahagi ng kaugalian equation na ginamit Fourier series ngunit Cauchy, Abel at Dirichlet had lahat ng mga tulis ang mga problema na kaugnay sa mga tagpo ng Fourier serye ng isang arbitrary function.