How Limits Are Evaluated Numerically
A limit asks: what value does f(x) get close to as x gets close to a — without ever needing to equal a? This tool builds an approach table: it evaluates the function at points like a ± 0.1, a ± 0.01, a ± 0.001, and watches where the outputs settle. If the left and right sides settle on the same number, that is (almost certainly) the limit.
The Classic 0/0 Case
Try (x²−1)/(x−1) as x → 1. Direct substitution gives 0/0, but the table shows values homing in on 2 — the hole in the graph is “filled” by the limit. Factoring the numerator first, (x−1)(x+1)/(x−1) = x+1, confirms it exactly.
When Limits Fail
- Jump: left and right approach different numbers — the two-sided limit does not exist.
- Blow-up: values grow without bound near a vertical asymptote — the limit is ±∞ (or does not exist as a finite number).
- Oscillation: sin(1/x) near 0 never settles — no limit.
Limits are the foundation of derivatives — see our derivative calculator.