Circle angles and tangents
Inscribed angles and radius-tangent perpendicularity.
Key knowledge
A Euclidean circle consists of points at one fixed positive radius from its center. An inscribed angle is half the central angle subtending the same arc, so an angle subtending a diameter is a right angle. The tangent at a circle point is perpendicular to the radius there.
Conditions and scope
- The inscribed angle's vertex lies on the opposite arc and differs from both endpoints; use the central angle for the intercepted arc, including a reflex angle when needed.
- The tangent is a straight line meeting the circle at exactly one point; these statements concern a circle in a Euclidean plane.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Inscribed angles and radius-tangent perpendicularity.
2026-10-10 · Independent Physics and Measurement reference editor (AI editorial bounded review). Exact bounded introductory reference claims and this practical concept inventory are approved after closure. Existing university/research proof and source scopes remain separate; no universal knowledge-completeness or experimental-validation assertion.
Foundational review
2026-10-10 · Independent AI editorial inspection of this new compact reference entry, its equations, applicability, sources and knowledge connections.
Sources from other places
Agreement within this scope
Inscribed angles versus corresponding central arcs, right angles on a diameter and radius–tangent perpendicularity.
The source includes reflex central angles; tangent perpendicularity is assumed within this chapter.
Siyavula Education and Everything Maths textbook contributors
- Mathematics XI · Circle geometry South AfricaEnglish
§8.2 Axioms; Centre/circumference theorem; Worked example 2; Reflex-angle exercises; Tangents
- Mathematics XI · Circle geometry
Entry details
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- foundation-math-circle-angle-tangent
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- foundations-audit.1
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- Foundational core completion