I can't say I've ever done calculus on a fractal, but my guess is that most fractals have a fixed surface area ratio. Since fractals have infinite textural dept

I can't say I've ever done calculus on a fractal, but my guess is that most fractals have a fixed surface area ratio. Since fractals have infinite textural depth, there's a hard limit to their surface area compared to the overall area. But what you're asking about is the inaccuracies in the Reimann Integral https://en.m.wikipedia.org/wiki/Riemann_integral https://en.m.wikipedia.org/wiki/Riemann_integral The short version is that you pick a reasonably small size for your rectangles, and it mostly averages out. The discrepancy is so small that it can largely be ignored. But for argument's sake, you can simply imagine infinitely many infinitely small rectangles. That will fit the curve perfectly, but is impractical to compute. So we accept the slightly less accurate value.