Triangles
Concept Map
Additional Resources
OER
- Web resources:
- Bright Hub Education - Basic concepts of triangles,Types of triangles,Angle sum property,Exterior and interior angle relation
- Folioz - Inequalities in triangle, Investigate the relationship between the sides and angles in a triangle
- JsunilTutorial - Test papers for triangles
- Books and journals
- Textbooks
- NCERT Textbooks – Class 9
- Karnataka Govt Text book – Class 8
- Syllabus documents
Non-OER
- Web resources:
CPALMS -Introduction to triangles as a closed three sided figure,Inequalities in triangles
- Books and journals
- Textbooks
- Syllabus documents (CBSE, ICSE, IGCSE etc)
Learning Objectives
- Identify a triangle
- Recognize interior and exterior angles
- Classifying types of triangles
- Recognize the angle sum property
- Establish relation between interior and exterior angles
Teaching Outlines
Concept #1. Formation of a triangle, elements of a triangle and its measures
- A triangle is a three sided closed figure.
- It is one of the basic shapes in geometry.
- It triangle is a polygon with three edges and three vertices.
- There are three angles in a triangle formed at the three vertices of the triangle.
- Interior and exterior angles in a triangle at a vertex, together form a linear pair.
Activities
- Formation of a triangle
- Elements of a triangle
- Measures in triangle
- Interior and exterior angles in triangle
Concept 2: Types of triangles based on sides and angles
Types of triangles based on angles in the triangle
- Acute triangles are triangles in which the measures of all three angles are less than 90o.
- Obtuse triangles are triangles in which the measure of one angle is greater than 90o.
- Right triangles are triangles in which the measure of one angle equals 90 degrees.
Types of triangles based on sides in the triangle
- Equilateral triangles are triangles in which all three sides are the same length.
- Isosceles triangles are triangles in which two of the sides are the same length.
- Scalene triangles are triangles in which none of the sides are the same length.
Activities
Concept 3: Angle sum property
Activity No # 7 : Click here [1]
Angle sum property