Mathematics
Grade 6
15 min
Identify and classify polygons
Identify and classify polygons
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1
Introduction & Learning Objectives
Learning Objectives
Define what a polygon is based on its key characteristics.
Identify whether a given two-dimensional figure is a polygon or not.
Count the number of sides and vertices of a polygon.
Classify polygons by their number of sides (e.g., triangle, quadrilateral, pentagon, hexagon, octagon).
Distinguish between regular and irregular polygons.
Differentiate between convex and concave polygons.
Have you ever noticed the shapes around you? 🏠 From the tiles on your floor to the signs on the road, geometry is everywhere! What makes some shapes 'polygons' and others not?
In this lesson, we'll explore the fascinating world of polygons. You'll learn how to identify these special two-dimensional figures, understand their parts, and classify them base...
2
Key Concepts & Vocabulary
TermDefinitionExample
PolygonA closed two-dimensional figure made up of three or more straight line segments that do not cross each other.A square, a triangle, and a stop sign (octagon) are all polygons.
SideA straight line segment that forms part of the boundary of a polygon.A triangle has 3 sides. A square has 4 sides.
Vertex (plural: Vertices)A point where two sides of a polygon meet. It's like a corner of the shape.A triangle has 3 vertices. A square has 4 vertices.
Regular PolygonA polygon where all sides are equal in length AND all interior angles are equal in measure.An equilateral triangle (all sides and angles equal) or a square (all sides and angles equal) are regular polygons.
Irregular PolygonA polygon where not all sides are equal in length, or not all interior angles ar...
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Core Formulas
Polygon Identification Rule
A figure is a polygon if and only if it meets ALL of these conditions: 1. It is a closed figure. 2. It is made up entirely of straight line segments. 3. The line segments do not cross each other. 4. It has at least three sides.
Use this rule to determine if any given 2D shape qualifies as a polygon. If any condition is not met, it's not a polygon.
Polygon Classification by Number of Sides
Polygons are named based on the number of sides they have:
- 3 sides: Triangle
- 4 sides: Quadrilateral
- 5 sides: Pentagon
- 6 sides: Hexagon
- 7 sides: Heptagon
- 8 sides: Octagon
- 9 sides: Nonagon
- 10 sides: Decagon
To classify a polygon, simply count its sides. The number of sides will always be equal to the number of vertices.
Regular vs. Irregula...
5 more steps in this tutorial
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Challenging
Which of the following combinations of classifications is impossible for a single polygon to have?
A.Irregular and Concave
B.Regular and Convex
C.Regular and Concave
D.Irregular and Convex
Challenging
A geographer is mapping a plot of land. The shape of the plot is a polygon with one interior angle measuring 210 degrees. What can you definitively conclude about this polygon?
A.It must be a regular polygon.
B.It must be a concave polygon.
C.It must be a convex polygon.
D.It must be a hexagon.
Challenging
If you can draw a straight line segment connecting any two vertices of a polygon, and that line segment never goes outside the polygon, what MUST be true about the polygon?
A.It must be a convex polygon.
B.It must be a regular polygon.
C.It must be a triangle.
D.It must be a concave polygon.
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