ABSTRACT
Various integral transforms have already been introduced and studied for the real variable case–Fourier transforms in Section 2.9 and Fourier Bessel transforms in Section 4.13 and at the end of Section 6.3. We know that these transforms appear naturally in the solution by separation of variables of partial differential equations involving the Laplacian, and that the integral transforms, rather than a summation of discrete eigenfunctions, appear when we deal with an infinite rather than a finite region.
