Classification of Polygons
What is a Polygon?
A polygon is a closed shape made up of straight line segments.
Sides are the line segments; vertices are the points where sides meet.
Important: The number of sides equals the number of vertices.
Types of Polygons by Number of Sides
- Triangle: 3 sides and 3 vertices
- Quadrilateral: 4 sides and 4 vertices
- Pentagon: 5 sides and 5 vertices
- Hexagon: 6 sides and 5 vertices
- Heptagon: 7 sides and 7 vertices
- Octagon: 8 sides and 8 vertices
Special Types of Triangles
By sides:
- Equilateral: All 3 sides are equal
- Isosceles: 2 sides are equal
- Scalene: All sides are different
By angles:
- Right: Has one 90° angle
- Acute: All angles are less than 90°
- Obtuse: Has one angle greater than 90°
Examples: Triangle Classification
By sides
By angles
Challenge: Can a triangle be both right and isosceles? Yes—place the right angle at the vertex where the two equal legs meet the hypotenuse. Try it in the Triangle Classifier below.
Special Types of Quadrilaterals
- Square: All sides equal, all angles 90°
- Rectangle: Opposite sides equal, all angles 90°
- Rhombus: All sides equal
- Parallelogram: Opposite sides parallel and equal
- Trapezoid: Only one pair of opposite sides parallel