Triangles

Additional Resources

OER

1. List web resources with a brief description of what it contains; how it can be used and whether it can be by teacher/ student or both
2. Books and journals
3. Textbooks
4. Syllabus documents

Non-OER

1. List web resources with a brief description of what it contains; how it can be used and whether it can be by teacher/ student or both
2. Books and journals
3. Textbooks
4. Syllabus documents

Learning Objectives

Concept #1. Formation of a Triangle, elements of a triangle and its measures

1. A triangle is a three sided closed figure.
2. It is one of the basic shapes in geometry.
3. It triangle is a polygon with three edges and three vertices.
4. There are three angles in a triangle formed at the three vertices of the triangle.
5. Interior and exterior angles in a triangle at a vertex, together form a linear pair.

Activity No # 1 : Formation of a triangle

Formation of a triangle

• Objectives

1. Understand formation of triangles
2. Recognize elements of triangle
3. Introduce concepts of exterior angle.

• Pre-requisites

Prior knowledge of point, lines, angles, parallel linesResources needed

• Resources needed

1. Digital : Computer, geogebra application, projector.
2. Non digital : Worksheet and pencil
3. Geogebra files : “1.Introduction to a triangle.ggb”

• How to do

1. Use the geogebra file to illustrate.
2. How many lines are there? Are the lines meeting?
3. Are the two lines parallel? How can you say they are parallel or not?
4. How many angles are formed at the point of intersection?
5. What is the measure of the total angle at the point of intersection of two lines?
6. Of the four angles formed which of the angles are equal? What are they called?
7. Do the three intersecting lines enclose a space? How does it look? It is called a triangle.
8. What are the points of intersection of these three lines called?
9. The line segments forming the triangle are called sides.
10. How many angles are formed when three lines intersect with each other?
11. How many angles are enclosed by the triangle?

• Evaluation at the end of the activity

1. Can there be a closed figure with less than three sides?
2. Can the vertices of the triangle be anywhere on a plane?
3. What will happen if the three vertices are collinear?