Introduction to history

OER

 * Web resources:
 * Wikipedia, the free encyclopedia


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


 * Syllabus documents

Non-OER

 * Web resources:
 * Historical thinking : blurb
 * 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.

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 Types of triangles based on sides in the triangle
 * 1) Acute triangles are triangles in which the measures of all three angles are less than 90o.
 * 2) Obtuse triangles are triangles in which the measure of one angle is greater than 90o.
 * 3) Right triangles are triangles in which the measure of one angle equals 90 degrees.
 * 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.

Activities

 * 1) Angle sum property:

Activities

 * 1) Relation between interior and exterior angles in triangle