Approximations
Build a useful estimate, compare a correction with a stated reference scale, and check what is lost when you leave out a term.
Key knowledge
The small-angle approximation sin θ ≈ θ uses θ in radians and is useful near θ = 0. Its error increases as the angle grows; it is not an equality for arbitrary angles.
Values and equations
sin θ ≈ θ
- θ
- Small angle expressed in radians rad
Conditions and scope
- θ is measured in radians.
- The acceptable angular range depends on the error tolerance of the calculation.
Sources · 8
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
- University Physics Volume 1, 1.5 Estimates and Fermi CalculationsWilliam Moebs; Samuel J. Ling; Jeff Sanny — OpenStax, Rice UniversityTextbook chapter
- Physics, 1.3 The Language of Physics: Physical Quantities and Units — Using Scientific Notation with Physical MeasurementsPaul Peter Urone; Roger Hinrichs — OpenStax, Texas Education AgencyTextbook chapter
- 18.01 Single Variable Calculus, Supplementary Notes, A. ApproximationsDavid Jerison and Arthur Mattuck (course-reader attribution) — Massachusetts Institute of Technology, Department of MathematicsTeaching resource · PDF
- Mathematics, Class XI, Chapter 7: Binomial Theorem, 7.1 Introduction and introductory identity block in 7.2National Council of Educational Research and Training (NCERT), IndiaTextbook chapter · PDF
- Asymptotic and Perturbation Methods, Chapter 1, 1.1 IntroductionVictor Ivrii — University of Toronto, Department of MathematicsTextbook chapter
- Cálculo I · Agenda 08: Limites fundamentaisJean Cerqueira Berni, Universidade de São PauloTeaching resource · PDF
Evidence and review
OpenStax 15.4, small-angle approximation and its range in pendulum modeling.
2026-10-10 · One explicit approximation and its domain only; no general error bound is certified for other models.
Foundational review
2026-10-10 · Fresh primary-source inspection of the complete compact record, including every statement, equation, quantity and material condition, followed by independent AI editorial review. This check does not certify all linked lessons or every passage of every cited publication.
Sources from other places
Scope or convention differs
The radian limit sin(x)/x tends to one near zero.
This supports small-angle approximation, without supplying a universal finite-angle error tolerance.
Universidade de São Paulo, Instituto de Matemática e Estatística
- Cálculo I · Agenda 08: Limites fundamentais BrazilPortuguese
§2 Limites fundamentais, pp.6–7
- Cálculo I · Agenda 08: Limites fundamentais
Related articles
Approximation methods and perturbative thinking ↗Entry details
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