# Classifying polygons

### Classifying polygons

#### Lessons

In this lesson, we will learn:

• How to name polygons: triangles, quadrilaterals, pentagons, hexagons, heptagons, and octagons
• How to classify regular vs. irregular polygons
• How to read markings on polygons: hashmarks for congruent sides, semicircles for congruent angles, arrows for parallel sides, and squares (right angles) for perpendicular sides

Notes:

• Polygons are 2D shapes with straight sides only. All polygons have sides (straight lines/edges) and vertices (corners/points where sides meet).

• Polygons are named by the number of sides they have: • Polygons can be regular or irregular. Regular polygons have congruent sides and angles; all sides and all angles are equal. Irregular polygons do not have same size sides and angles. • Congruent sides can be shown with hashmarks (matching lines on the sides that are equal)
• Congruent angles can be shown with either semicircles with hashmarks, or with concentric circles • Introduction
Introduction to Classifying Polygons:
a)
What are polygons?

b)
Names of different polygons based on number of sides (triangles to octagons)

c)
Regular or irregular polygons: markings for congruent sides and angles

d)
Understanding markings for parallel and perpendicular sides in polygons

• 1.
Sides and vertices in polygons
Count the number of sides and vertices in the polygon. Circle the vertices and check mark the sides to help keep track.
a) b) c) • 2.
Classifying polygons by name and regularity
Look at the picture of the shape and write:
• the name of the polygon
• and if it is regular or irregular
a) b) c) d) e) • 3.
Congruent sides and angles in polygons
Draw markings for any pairs of equal sides and/or angles
a) b) c) • 4.
Parallel sides in polygons
Mark the parallel sides with matching arrows on each pair. How many pairs of sides are parallel?
a) b) c) 