11.1: Triangles

1) Lesson Objectives:

You should be able to

• identify different types of triangles

• know the properties of triangles

• know angle sum of triangles

• know exterior angles of triangles

Terminologies

• Equilateral triangles

• Isosceles triangles

• Scalene triangles

• Acute-angles triangles

• Right-angled triangles

• Obtuse-angled triangles

• Vertex / vertices

• Interior angles

• Exterior angles

Properties of angles in triangles:

• Angle sum of triangle

• Exterior angle of triangle

A: Classification of triangles

Read and try to understand Textbook 1B explanations and worked examples: pg 98 to 99.

Fill in the blanks (grey coloured box) in the table for pg 98.

B: Basic properties of triangle

Read and try to understand Textbook 1B explanations and worked examples: pg 99 to 100.

C: Angle sum of triangle

Read and try to understand Textbook 1B explanations and worked examples: pg 101.

Fill in the blanks (grey coloured box) in the Thinking Time for pg 101.

D: Exterior angles of triangle

Read and try to understand Textbook 1B explanations and worked examples: pg 102 to 103.

Fill in the blanks (grey coloured box) in the Thinking Time for pg 102.