Triangles

Concept Map

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Additional Resources

OER

• Web resources:

1. Bright Hub Education - Basic concepts of triangles,Types of triangles,Angle sum property,Exterior and interior angle relation
2. Folioz - Inequalities in triangle, Investigate the relationship between the  sides and angles in a triangle
3. JsunilTutorial - Test papers for triangles

• Books and journals
• Textbooks
• NCERT Textbooks – Class 9

1. 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

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.

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.