Explore the derivation of a closed form for the infinite sum cos(n)/n^4 using Fourier series in this 25-minute mathematics video. Delve into topics such as Fourier expansion, repeated functions, integration by parts, and B coefficients. Follow along as the instructor guides you through the step-by-step process, from the initial setup to the final form of the solution. Gain insights into advanced mathematical techniques and enhance your understanding of infinite series and Fourier analysis.