# The Basel Problem / Zeta (2) and Wallis’s Product (VIDEO!)

In 1644, Italian mathematician Mengoli asked for the exact value of the infinite sum of the reciprocals of the square numbers: 1 + 1/4 + 1/9 + 1/16 + 1/25 + … = ?? He knew that the sum was bounded and wanted to know its value. Some ninety years later a young Leonhard Euler solved the problem and showed the exact answer to be (pi^2)/6. This is how Euler did it. (We’ll also derive Wallis’s product as a bonus!)