Once there was a variable, and the variable's name was `x`. Ze was used in a function named `f`. In this function, `x` was squared, subtracted from one, and then square rooted. A beautiful graph the function made – a semicircle, like a rainbow. One could almost see the pot of gold at `f`(±1). Suddenly the graph was filled in. `x` noticed that there was an odd line, curved at the end, before f, with numbers on it. Suddenly, `x` felt an odd sensation – `f` was disappearing, being simplified away. What was left was half a pi – a delicious-looking rhubarb pie, to be specific. Not just *any* rhubarb pie, no, this was a Bee-Bop-a-Re-Bop rhubarb pie, the kind that supports Prairie Home Companion. `x` looked back on zir life, wondering if there was a long chain of events leading to a bad situation which would warrant said pie. Ze remembered the time when they took the derivative of `f`. They separated out the 1 + `x`^{2} from the square root, called it the "chain rule" or something. Perhaps that could be the chain of events? `g`'(`x`)`f`'(`g`(`x`))? Or not. That just seemed to end up in... nothing. They were back where they started. Nothing ever changed... except for `x`'s value. `x` looked back... ze liked being zero, then the function was nice and positive, even if only positive one. They never seemed to get higher than that. So `x` ate the half pi. The end.

(Author's note: Integral from -1 to 1 of the square root of 1 - `x`^{2} is, indeed, π÷2.)