An Elementary Way to Calculate the Gaussian Integral

from blog Fred Akalin, | ↗ original
While reading Timothy Gowers's blog I stumbled on Scott Carnahan's comment describing an elegant calculation of the Gaussian integral \[ ∫_{-∞}^{∞} e^{-x^2} \, dx = \sqrt{π}\text{.} \] I was so struck by its elementary character that I imagined what it would be like written up, say, as an extra credit exercise in a single-variable calculus...