## Pace’s derivation of Euler’s sum of reciprocals of squares

One of my favourite identities in mathematics is the sum of the reciprocal of the squares $$1 + \frac{1}{4} + \frac{1}{9} + \frac{1}{16} + \cdots = \frac{\pi^2}{6}.$$ This summation, first derived by Euler, is known as the Basel problem. It is perhaps the most natural sum to consider after the harmonic sum $1 + 1/2 […]