Mathematics
Improper Integrals and Their Evaluation Using Limits
Quick fact
An improper integral can sometimes assign a finite area to a region that extends infinitely far or has an infinite spike, thanks to the power of limits—a concept that seems to defy our intuition about infinity.
Why this is interesting
You know how to find the area under a curve, but what if the curve stretches to infinity or shoots up past the sky? How can you possibly measure that?