b2KIT

Limit Explorer

Investigate limits visually by zooming into function behavior near a point. Shows left/right limits, holes, and asymptotes.

Tested tool guide Tested browser tools Checked August 16, 2026

What Limit Explorer does, with a checked example

Limit Explorer centers a function graph on an approach point and lets you zoom in to inspect what happens from smaller and larger x-values. Its separate left-hand and right-hand results help distinguish an ordinary limit, a jump, a hole, and unbounded behavior near a vertical asymptote. The important surprise is that the limit concerns nearby values, not necessarily the value at the point. A finite limit can exist even when the function is undefined there.

Worked example

A concrete input and expected output from the current implementation.

Input

Function: (x^2 - 1)/(x - 1); point: x = 1

Expected output

Left-hand limit: 2; right-hand limit: 2; two-sided limit: 2; hole at (1, 2); f(1) is undefined.

For every x other than 1, factoring and canceling x - 1 reduces the expression to x + 1. Approaching 1 from either side therefore gives 2, while substitution into the original denominator gives zero.

How the result is produced

1

Compare both approaches

After a function and approach point are selected, the graph can be examined at progressively smaller horizontal distances from that point. The left-hand result follows x-values below the target, while the right-hand result follows values above it. A two-sided limit exists only when those approaches agree; disagreement remains visible instead of being combined into one value.

2

Separate limits from values

The explorer treats nearby behavior separately from the function's value exactly at the target. A canceled factor can leave an undefined point even though surrounding values approach one finite height, producing a hole. If magnitudes increase without bound near the target, the display instead identifies asymptotic behavior. This distinction is essential when checking continuity.

Good uses

  • Checking whether a rational expression with a canceled factor has a removable discontinuity and identifying the hole's height.
  • Comparing the two sides of a piecewise function before deciding whether its two-sided limit exists.
  • Inspecting how a function behaves near a suspected vertical asymptote, including whether its two sides head in different directions.

Limits and checks

  • A graph that appears to settle is visual evidence, not a formal proof. Rapid oscillation or behavior confined to a very narrow interval may require further zooming and algebraic analysis.
  • A hole's y-coordinate describes the approached value. It does not mean the original function is defined at that coordinate, or that the discontinuity has been filled.
  • A two-sided limit requires meaningful approach behavior from both sides of the point. At a domain endpoint, only one side may contain allowable x-values.

Common questions

Can the limit exist when the function is undefined at the point?

Yes. The explorer examines values near the target, so both sides can approach the same number while the target itself is excluded. The example above approaches 2 even though its original expression divides by zero at x = 1. This is shown as a hole rather than as a failure of the limit.

Does a matching left-hand and right-hand limit prove continuity?

No, not by itself. Matching sides establish the two-sided limit, but continuity at the point also requires the function to be defined there and to have that same value. A hole therefore fails continuity despite matching limits. The visual result can guide the check, while a proof may still require symbolic reasoning.

References and verification

The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.

Related Tools