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AP® Calculus BC · Unit 10 · Topic 10.12

Lagrange Error Bound: Topic Checklist (Calculus BC 10.12)

Specific “I can…” statements for the Lagrange error bound, each linked to the guide section and practice question that shows whether you can really do it.

BC-only material. Work through the list without notes. If you cannot do a statement, follow its link, then come back. Guide = study guide; Practice = practice questions. Prerequisites (Topics 10.10 and 10.11) are on the Calculus BC roadmap.

Understanding

  • I can state the Lagrange error bound and say what n, M and f⁽ⁿ⁺¹⁾ stand for. (Guide: “The Lagrange error bound”; Practice Q1)
  • I can explain that the bound is a guarantee, not the actual error, and that the true error is often smaller. (Guide: Worked example 2; Practice Q4)
  • I can explain why a bigger M is safe but a smaller M than the true maximum is not. (Guide: “Choosing M”; Practice Q2, Q5(c))

Skills

  • I can find a valid M for sin, cos, eˣ and for derivatives that only increase or only decrease on the interval. (Guide: “Choosing M”; Practice Q2, Q5(c), Q7(a))
  • I can calculate the Lagrange error bound for a given polynomial and point. (Guide: Worked example 1; Practice Q1, Q6(c))
  • I can use a bound to write an interval that must contain the true value. (Guide: Worked example 1(c); Practice Q4, Q6(d))
  • I can find the smallest degree that the Lagrange bound guarantees for a required accuracy. (Guide: Worked example 2; Practice Q7(a))
  • I can use the alternating series error bound for a Taylor estimate when its conditions hold. (Guide: “The alternating series error bound as an alternative”; Practice Q3, Q7(c))

Reasoning

  • I can show that an error is less than a given number by stating the bound and then the comparison. (Guide: “When M is given”; Practice Q5(c), Q6(c))
  • I can decide whether an estimate is an overestimate or an underestimate, using the sign of the first omitted term or of f⁽ⁿ⁺¹⁾. (Guide: Worked example 1 checks; Practice Q7(c))
  • I can use an error interval to justify a conclusion, such as the sign of a function value. (Practice Q6(d))
  • I can spot when Pₙ = Pₙ₊₁ and use the stronger bound. (Guide: sin 0.4 example; Practice Q7(b))

All ticked? Move on to Topic 10.13, Radius and Interval of Convergence of Power Series, or return to the Calculus BC roadmap.

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