- We derive the addition formulas for sine and cosine from the arithmetic of complex numbers .
- Firstly , in spherical coordinate system , the sovp formulation for the time - harmonic electromagnetic fields of the current dipole in conductive infinite - space is derived , using reciprocity theorem and transforming relations between special functions . then , selecting appropriate coordinate system , using superposition principle , the boundary - value problem of modified magnetic vector potential on the problem of a time - harmonic current dipole in spherical conductor is solved and analytical solution is obtained . finally , by means of the addition formulas of legendre polynomial and spherical harmonics function of degree n and order 1 , the analytical solution in spherical coordinate system specially located is transformed into that in spherical coordinate system arbitrarily located
- The addition formula of spherical harmonics function of degree n and order 1 is derived using the relations between coordinate varieties after coordinate rotating and the property of the associated legendre polynomial . the relations among the magnetic vector potential , the modified magnetic vector potential and the second - order vector potential ( sovp ) are shown going forward one by one . it is explained that the solutions of electromagnetic fields in different coordinate systems can be transformed and an example having analytical solution is given