The Basel Problem: A double integral solution

The Basel problem is an all-time classic math problem. Among all of its solutions, my favorite is based around the computation of a double integral. Here is a link to the source of this solution: https://www.researchgate.net/publicat.... In fact, using the same technique from the video, one can evaluate the infinite sum of 1/n^(2k) for any (positive integer) k! A slightly different double integral solution can be found here: https://analysisofmath.wordpress.com/.... Obviously, more reading about the problem can be found here: https://en.wikipedia.org/wiki/Basel_p...