Subject : Mathematics
Class : Basic 6 / Primary 6 /Grade 6
Term : Third Term / 3rd Term
Week : Week 5
Topic : Types of Triangles
Behavioural Objectives : At the end of the lesson, the pupils should be able to
- Explain the meaning of triangles
- Give examples of triangles
- Mention types of triangles
- Say the properties of triangles
Previous Knowledge : Pupils have previous knowledge of Polygons and plane figure that was taught in the previous lesson
Instructional Materials :
- Wall Posters
- Related Online Videos
- Role Playing
- Scheme of Work
- Online Information
- 9 Year Basic Education Curriculum
Types of Triangles
Triangles are three sided shapes . They have three sides and three angles . The angles in the triangles are called interior angles while the angles that are outside are called exterior angles . A triangle can also be formed by using a diagonal line to divide a square or a rectangle diagonally . . These are the types of triangles that we have
- A right angled triangle : This is a triangle that has one of its interior angles equal to 90 degrees
- An equilateral triangle : This is a triangle that has all the three angles and sides equal
- A Scalene triangle : This type of triangle has no equal sides
- An Isosceles triangle : This is a triangle that has two equal sides or angles
The area of a triangle is obtained when the value of half of the base is multiplied by the height
Area = 1 / 2 × base × height.
The line that is directly opposite the right angle is called the Hypotenuse .
Mental Sums on Types of Triangles
1. What is a triangle
2. Define scalene triangle
3. Triangles are three sides shapes . True or false
4. What is an equilateral triangle
5. A plane shape that has three sides and angles is called a ________________
6. The value of the right angle in a triangle is equal to _______________________
7. The angle of a triangle is in the ratio of 2: 3: 4. Find the measure of each angle of the triangle.
8. One of the two equal angles of an isosceles triangle measures 55°. Determine the other angles.
9. The perimeter of a triangle is 24 cm. Two of its sides are 8 cm and 9 cm. Find the length of its third side.
10. Each side of a ∆ is one third of its perimeter. What kind of triangle is this?
11. One of the acute angles of a right triangle is 48°. Find the other acute angle.
12. Say whether the following statements are true or false:
(a) All the angles of an isosceles triangle are equal.
(b) If one angle of a triangle is obtuse, the other two angles must be acute.
(c) A right triangle can be equilateral.
(d) Quadrangular triangle has its three sides also equal.
(e) A triangle can have two obtuse angles.
The topic is presented step by step
The class teacher revises the previous topics
He introduces the new topic
The class teacher allows the pupils to give their own examples and he corrects them when the needs arise
Prepare for the next lesson by reading about
Types of Angles and Shapes
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