Time-dependent Diffusion: Fourier Trick

This lecture covers the determination of coefficients in a sine series using the Fourier Trick, focusing on time-dependent diffusion problems in a Cartesian coordinate system. The instructor explains the process step by step, from finding the base solutions via separation of variables to solving the partial differential equations (PDE) and boundary conditions. The lecture emphasizes the importance of correctly determining the coefficients to obtain the general solution. Various trigonometric identities are used to simplify the calculations and express the solutions in terms of sines and cosines.