Explanation
A polygon is a \(2D\) closed shape made of straight line segments.
To be a polygon, a shape must:
✔ be closed
✔ be made of straight line segments
✔ be two-dimensional (\(2D\))
A shape is not a polygon if:
✘ it is open
✘ it contains a curve
✘ it is a three-dimensional shape
Examples of polygons include triangles, quadrilaterals, and pentagons.
Examples of shapes that are not polygons include circles and cubes.
Formula / Rule
A polygon must satisfy all three conditions:
- Closed shape
- Straight sides
- Two-dimensional (\(2D\))
Examples
Example 1
Is a triangle a polygon?
Yes.
A triangle is closed and made of three straight sides.
Therefore, a triangle is a polygon.
Example 2
Is a circle a polygon?
No.
A circle has a curved boundary.
Therefore, a circle is not a polygon.
Example 3
Is an open shape with four straight sides a polygon?
No.
The shape is not closed.
Therefore, it is not a polygon.
Example 4
Is a pentagon a polygon?
Yes.
It is closed and made of five straight sides.
Therefore, a pentagon is a polygon.
Example 5
Is a cube a polygon?
No.
A cube is a three-dimensional shape.
It is called a polyhedron, not a polygon.
Video Explanation
Practice
Continue Learning
- Polygons (Basics)
- Types of Polygons
- Is this a Polygon (Current lesson)