Angle sums of polygons
Interior and exterior angle sums for convex polygons.
Key knowledge
A convex Euclidean polygon with n vertices has interior angle sum (n−2)π radians. Its exterior turning angles, taken consistently around the boundary, sum to 2π.
Values and equations
Σ_i α_i=(n−2)π; Σ_i (π−α_i)=2π
- n
- Number of polygon vertices, an integer at least 3
- α_i
- Interior angle at vertex i, for i=1,…,n rad
Conditions and scope
- Use a nondegenerate convex simple polygon with integer n≥3.
- Each exterior turning angle is the supplement of its interior angle; do not mix different choices of exterior angle.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Interior and exterior angle sums for convex polygons.
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
Scope or convention differs
A consistent walk around a convex polygon turns through one full turn.
This corroborates the exterior sum; the interior (n−2)π formula remains outside the inspected section.
National Council of Educational Research and Training
- Mathematics VIII · Understanding quadrilaterals IndiaEnglish
§3.1.1 p.21; §3.2 p.23 (PDF p.3)
- Mathematics VIII · Understanding quadrilaterals
Entry details
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- foundation-math-polygon-angle-sums
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- foundations-audit.1
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- Foundational core completion