epsilon_delta_bounding

Construct explicit δ(ε) or N witnesses for Lean 4 / mathlib4 limit proofs.

1|Updated Mar 14, 2026
One-click install
npx skills add https://github.com/bneb/perqed --skill epsilon-delta-bounding
Or copy as Structured Prompt for Agent
Please help me install this Agent Skill.
Skill: epsilon_delta_bounding
Source: https://github.com/bneb/perqed/tree/main/.agents/skills/epsilon_delta_bounding
Command: npx skills add https://github.com/bneb/perqed --skill epsilon-delta-bounding

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

The epsilon-delta method formalizes the intuitive notion of "closeness" in analysis. To prove lim_{x→a} f(x) = L, one must exhibit δ(ε) > 0 such that 0 < |x - a| < δ → |f(x) - L| < ε. The same structure extends to sequences, uniform continuity, and convergence in metric spaces.

Core Features & Use Cases

  • Construct explicit δ(ε) or N witnesses to certify limits, continuity, and convergence within Lean 4 / mathlib4.
  • Leverage Lean tactics like norm_num, positivity, linarith, and gcongr to close arithmetic bounds automatically.
  • Provide end-to-end templates and examples for common limit and continuity proofs in Lean 4.

Quick Start

Provide a Lean 4 goal for a limit or convergence and request an explicit δ(ε) witness to complete the proof.

Frequently Asked Questions about epsilon_delta_bounding

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I construct an explicit delta witness for epsilon-delta proofs in Lean 4?

To construct an explicit delta witness for epsilon-delta proofs in Lean 4, you provide a specific δ(ε) bound and apply tactics like norm_num, positivity, and linarith to close algebraic inequalities and certify limits.

Can I use mathlib4 to formalize sequence convergence with explicit N witnesses?

Yes, you can use mathlib4 to formalize sequence convergence by constructing explicit N witnesses, applying Lean 4 tactics to close arithmetic bounds and verify that sequence terms satisfy convergence criteria.

What is the best way to prove limits in Lean 4 using the epsilon-delta method?

The best way to prove limits in Lean 4 using the epsilon-delta method is to exhibit δ(ε) > 0 such that 0 < |x - a| < δ implies |f(x) - L| < ε, leveraging tactics like gcongr to automate closing algebraic inequalities.

Do I need Lean 4 tooling and mathlib4 imports to formalize continuity proofs?

Yes, formalizing continuity proofs with explicit bounds requires Lean 4 tooling and mathlib4 imports to construct δ(ε) witnesses that guarantee |f(x) - L| < ε across metric space contexts.

Why does my epsilon-delta proof fail when closing algebraic inequalities in Lean 4?

Your epsilon-delta proof may fail in Lean 4 if the explicit δ(ε) bounds are insufficient to close algebraic inequalities, requiring tactics like linarith or positivity to automatically verify that |f(x) - L| < ε holds.

Does the epsilon-delta bounding approach work for uniform continuity in metric spaces?

Yes, the epsilon-delta bounding approach extends to uniform continuity and convergence in metric spaces by constructing explicit δ(ε) or N witnesses within Lean 4 and mathlib4 to certify the bounds.