Triangles

OER

 * Web resources:
 * Wikipedia, the free encyclopedia : The website gives a comprehensive information on triangles from basics to in depth understanding of the topic.
 * cbsemathstudy.blogspot.com : The 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


 * Syllabus documents

Non-OER

 * Web resources:
 * Bright hub education : The 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.
 * UrbanPro : This website gives downloaded worksheets for geometry construction.
 * AglaSem Schools : This website lists important questions for math constructions.


 * Books and journals
 * Textbooks:
 * Karnataka Govt Text book – Class 8 : Part 1, Part 2
 * 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

Concept 1: Formation of a triangle, elements of a triangle and its measures
Introducing formation of a shape with minimum number of lines and the space enclosed forms a geometric shape.The key geometric concepts that are associated with it and its properties are elaborated.

Formation of a triangle
A plane figure formed by three intersecting lines.

Elements and measures in triangle
Parameters that are associated and measured in a triangle.

Interior and exterior angles in triangle
Angles that are formed when a triangle is formed.

Concept 2: Types of triangles based on sides and angles
Triangles can be based on its elements such as sides and angles. Students are able to recognize these formations.

Types of triangles based on sides
Formation of a triangle depends on measures of sides.

Types of triangles based on angles
Formation of a triangle depends on measures of angles.

Concept 3: Theorems and properties
Properties of triangles are logically proved by deductive method. Relations ships between angles of a triangle when a triangle is formed are recognized and understood.

Angle sum property
Relation between angles formed inside a triangle

Exterior angle theorem
Relation between angles formed inside a triangles and angles outside a triangle

Concept 4: Construction of triangles
Constructing geometric shapes to precision using a scale and a compass helps in understanding of properties of the shape. Constructing geometric shapes with minimum number of parameters enhances thinking skills.

The following constructions are based on three essential parameters that are required for construction following the SSS, SAS and ASA theorems

Construction of a triangle with three sides
Construction of a triangle based on the SSS congruence rule

Construction of a triangle with two sides and an angle
Construction of a triangle based on SAS congruence rule

Construction of a triangle with two angles and included side
Construction of a triangle based on ASA congruence rule

Construction of a right angled triangle
Construction of a triangle based on RH congruence rule

Construction of a triangle with perimeter and base angles
Construction on a triangle with give parameters using SAS congruence rule

Construction of a triangle with a side, an angle and sum of two sides
Construction on a triangle with give parameters using SAS congruence rule

Construction of a triangle with a side, an angle and difference to two sides
Construction on a triangle with give parameters using SAS congruence rule