Triangles

Concept Map

[maximize][fold]

Additional Resources

OER

• Web resources:
  • Wikipedia, the free encyclopedia : This gives comprehensive information on triangles from basics to in depth understanding of the topic.
  • cbsemathstudy.blogspot.com : This website gives worksheets for the chapters that can be downloaded. Worksheets for other chapters can also be searched for which are listed based on class.

• Books and journals
• Textbooks
• NCERT Textbooks – Class 9
  • Karnataka Govt Text book – Class 8

• Syllabus documents

Non-OER

• Web resources:
  • Bright hub education : This website describes a lesson plan for introducing triangles and lists classroom problems at the end of the lesson that can be solved for better understanding.
  • CPALMS : The website gives lesson plan, activities and worksheets associated with triangles.

• Books and journals
• Textbooks
• Syllabus documents (CBSE, ICSE, IGCSE etc)

Learning Objectives

• Identifying a triangle and understanding its formation
• Recognizing all parameters related to triangles
• Understanding formation of triangles based on sides and angles
• Establishing relationship between parameters associated with triangles

Teaching Outlines

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.

Activities

1. Formation of a triangle: A plane figure formed by three intersecting lines.
2. Elements of a triangle: Terms that are associated with triangle.
3. Measures in triangle: Parameters that are measured in a triangle.
4. Interior and exterior angles in triangle: Angles formed when a triangle is formed.

Concept 2: Types of triangles based on sides and angles

Types of triangles based on angles in the triangle

1. Acute triangles are triangles in which the measures of all three angles are less than 90^o.
2. Obtuse triangles are triangles in which the measure of one angle is greater than 90^o.
3. Right triangles are triangles in which the measure of one angle equals 90 degrees.

Types of triangles based on sides in the triangle

1. Equilateral triangles are triangles in which all three sides are the same length.
2. Isosceles triangles are triangles in which two of the sides are the same length.
3. Scalene triangles are triangles in which none of the sides are the same length.

Activities

1. Types of triangles based on sides: Triangles formed are dependent on measures of sides.
2. Types of triangles based on angles: Triangles formed are dependent on measures of angles.

Concept 3: Theorems and properties

Activities

1. Angle sum property:
2. Relation between interior and exterior angles in triangle