Class VI

Chapter Triangle

Key Concepts Triangle as a three sided closed figure.

Components of a triangle.

Classification of triangle on the basis of

(a) sides and (b) angles

Interior and exterior of a triangle

Angular region of a triangle

Angle sum property of interior angles of a triangle

Side inequality property of a triangle.

Exterior angles

Exterior angle property of a triangle

Vocabulary used

Term/Definition/Example/Non-Example

Open and closed curves

Triangle

Scalene, isosceles, equilateral

Acute angled, right angled, obtuse angled

Interior

Exterior

Angular region

Inequality

Flow of Chapter Introduction of open and closed curve by showing different curves

Special type of closed curves ( rectilinear and non rectilinear, but the name is not to be mentioned in class 6) by showing figures

Concluding by saying, we will focus only on the figures made of line segments.

Classifying the following as three sided, four sided and five sided figures and introducing 3 sided closed figure as triangles

Particular names of all the figures given above as triangle, square, pentagon, hexagon, heptagon, octagon, nonagon, decagon etc

Classification of triangle on the basis of sides 1. scalene triangle 2. isosceles triangle 3. equilateral triangle Classification of triangle on the basis of angles 1. Acute angled triangle 2. Right angled triangle 3. Obtuse angled triangle

Worksheet 1

Worksheet 2 Classify the following on the basis of sides (scalene, isosceles and

equilateral)

Interior, exterior and angular region of a triangle

Worksheet 3

(fig 1 ) Fill in the blanks: Fig1: points in the interior of triangle: ______________________________ points in the exterior of triangle: ______________________________ Points on angular region: ___________________________________ ( fig 2) Mark the following in above triangle: 1. Vertices A,B and C 2. Points J, P on the angular region 3. Points M, K in the interior of triangle 4. Points L, S and E in the exterior of triangle.

Angle sum property of interior angles of a triangle

(by paper cutting and pasting activity)

Conclusion

Problems based on ASP Worksheet 4

Side inequality property of triangle

Problems based on side inequality of triangle Worksheet 5

Find if the we can construct a triangle with given sides

1. 5cm, 7cm, 4cm

2. 6cm, 6cm, 13cm

3. 12cm, 14cm, 15cm

Exterior angle property of a triangle

(by paper cutting and pasting activity)

Problems based on exterior angle property

Worksheet 6

(more questions can be added)

Common errors committed

Angle sum property sometimes is mixed with side inequality of triangles.

Enrichment /extended activities

Identify the triangles in the real world around (like: pyramid, in bridges etc), classify them in different types and verify angle sum property and side inequality property for them.