Kind of intentionally obtuse since they used eₑ as a variable and eₑₑ as another variable, and used (e-e) as an exponent a few times, which is basically the equivalent of multiplying by 1 in a fancy way. The first and last term also perfectly cancel out.
Wait... that's not an approximation at all! That equals exactly pi.
If I understand the math correctly, it's effectively a formula for the area of a unit circle.
That should be an approximation. To get exactly pi the range of both integrals should be from minus infinity to infinity like this.
It's the integral of the 2D Gaussian, which is fairly known.
For some reason in my head, "eeeeeeeeeeeee de eee de e" is the sounds a toddler makes when you take them to a play ground and they just start to run in wide arcs - unable to decide which piece of equipment to play on first.
So, of course, the integral of "eeeeeeeeeeeee de eee de e" would be the sound of them sleeping the car on the way home.
Could be the right hand side or the left hand side of an equation* or of an inequation** whatever.
(*) equations have "=" in middle
(**) inequations have "=<" (or ...) in middle.