Polygon perimeter and parallel-base areas
Boundary length and enclosed area measure different properties of a plane shape.
Key knowledge
A simple polygon's perimeter is the sum of its boundary side lengths. A rectangle with length L and width W has perimeter 2(L+W). A parallelogram's area is its base length times the perpendicular height. For a convex trapezoid, the area is half the sum of its two parallel base lengths times their perpendicular separation.
Values and equations
P=Σ(i=1 to n)s_i; P_rectangle=2(L+W); A_parallelogram=bh; A_trapezoid=(a+b)h/2
- P, P_rectangle
- Polygon boundary length and rectangle boundary length length
- n
- Number of polygon sides, an integer at least 3 1
- s_i
- Length of boundary side i, with i=1,…,n length
- L, W
- Positive rectangle length and width length
- a, b
- Trapezoid parallel base lengths; b also denotes the chosen parallelogram base in its separate formula length
- h
- Perpendicular height between the parallel base lines in the corresponding shape length
- A_parallelogram, A_trapezoid
- Enclosed areas of the corresponding plane regions length²
Conditions and scope
- Use nondegenerate Euclidean plane shapes and positive lengths expressed in a common unit. The polygon boundary does not cross itself.
- Height is perpendicular to the parallel base lines, rather than the length of a sloping side. Here a trapezoid has exactly one pair of parallel opposite sides.
- Perimeter has length units; area has square length units. A boundary length alone does not determine enclosed area.
Sources · 3
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
- Ganita Manjari, Grade 9, Part I, chapter 6: Measuring space, sections 6.1 and 6.7 (2026–27)National Council of Educational Research and Training, IndiaTextbook chapter · PDF
- Prealgebra 2e, 9.4: Perimeter and trapezoid areaLynn Marecek, MaryAnne Anthony-Smith and Andrea Honeycutt Mathis / OpenStaxTextbook chapter
- TIMES · Area, volume and surface areaAMSI and University of Melbourne, ICE-EMTeaching resource
Evidence and review
Boundary-length addition and Euclidean rectangle, parallelogram and trapezoid measure formulas within the stated geometric conditions.
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
Base times perpendicular height and trapezium mean-parallel-side times height areas.
The source’s trapezium wording leaves inclusive terminology open; repository perimeter formulas are outside these sections.
Australian Mathematical Sciences Institute and University of Melbourne
- TIMES · Area, volume and surface area AustraliaEnglish
Area of a parallelogram; Area of a trapezium
- TIMES · Area, volume and surface area
Entry details
Permanent link to this entry ↗- Record identity
- foundation-math-polygon-measures
- Revision
- foundations-audit.1
- Structured reference record
- Foundational core completion