Polygons
Polygons are closed, flat shapes with only straight sides. In Grade 6 Saxon Math Course 1, students learn the three requirements for a shape to be a polygon: it must be closed (no gaps), have straight sides (no curves), and be flat (two-dimensional). Circles are not polygons because their boundaries are curved. Polygons are named by their number of sides: triangle (3), quadrilateral (4), pentagon (5), hexagon (6), heptagon (7), octagon (8). This classification vocabulary is used throughout the geometry curriculum.
Key Concepts
New Concept Polygons are closed, flat shapes with straight sides. What’s next Next, we'll practice identifying, naming, and describing different types of polygons. You will also see worked examples using their properties.
Common Questions
What are the three requirements for a polygon?
It must be a closed shape, have only straight sides, and be flat (2-dimensional).
Is a circle a polygon?
No. A circle has a curved boundary, not straight sides, so it does not meet the polygon definition.
What is a pentagon?
A pentagon is a polygon with five sides and five vertices.
What is the difference between a regular and irregular polygon?
A regular polygon has all sides equal and all angles equal (like a square or equilateral triangle). An irregular polygon has sides or angles of different measures.
Name the polygon with eight sides.
An octagon — the same shape as a stop sign.