Polygons

Lesson 1 - Types of Polygons

A polygon is a closed shape with 3 or more sides. Each side is made from a line segment. Therefore, none of its sides is curved or circular. Along with sides, polygons also have vertices and angles. A vertex is where the line segments intersect while the angle is the space, measured in degrees, between two segments at each vertex. All polygons are 2 D shapes.

Polygons are named according to the number of sides they have. The polygon with the least number of sides is the triangle. A polygon can have an infinite number of sides.

Activity #1: Use the information in the chart above to complete the table below.

Activity #2: Use a combination of polygons to create 3 different compound shapes, e.g. a design of a house or drawing of an animal or person.

Lesson 2 - Types of Triangles

Let's answer the following questions from the video.

How would you describe a triangle? A triangle is a polygon that has _____ sides, _____ angles and _____ vertices.
Identify 2 ways in which triangles can be classified. Triangles are classified by their _________ and by their _________.
How would you describe an acute triangle? An acute triangle has 3 ________ angles.
How would you describe an obtuse triangle? An obtuse triangle has 1 __________ angle.
How would you describe a right triangle? A right triangle has ___________ angle.
How would you describe an equilateral triangle? An equilateral triangle has _____ equal sides and 3 equal ___________.
How would you describe an isosceles triangle? An isosceles triangle has ________ equal sides and _____ equal angles.
How would you describe a scalene triangle? A scalene triangle has _____ unequal sides and _____ unequal angles.

Equilateral, Isosceles and Scalene

There are three special names given to triangles that tell how many sides (or angles) are equal.

Select the button to complete a quiz.

Quiz

Activity: Draw then write the type for each triangle.

Identify by sides.

Lesson 3 - Finding the Missing Angles of Triangles

Add the 3 angles of each triangle and see what's special about the answers.

The video below explains how to find the missing angle of a triangle.

The 3 interior angles of a triangle always add up to 180⁰. No matter how big or how small the triangle is, the sum is always 180⁰. If we know the size of any 2 angles, we can make calculations to find the third angle.