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NCERT Class 7 Maths Textbook Chapter 7 With Answer PDF Free Download PDF Free Download
Chapter 7: Congruence of Triangles
7.1 Introduction
You are now ready to learn a very important geometrical idea, Congruence. In particular, you will study a lot about the congruence of triangles. To understand what congruence is, we turn to some activities.
The relation of two objects being congruent is called congruence. For the present, we will deal with plane figures only, although congruence is a general idea applicable to three-dimensional shapes also.
We will try to learn a precise meaning of the congruence of plane figures already known.
7.6 CRITERIA FOR CONGRUENCE OF TRIANGLES
We make use of triangular structures and patterns frequently in day-to-day life. So, it is rewarding to find out when two triangular shapes will be congruent.
If you have two triangles drawn in your notebook and want to verify if they are congruent, you cannot every time cut out one of them and use the method of superposition.
Instead, if we can judge congruency in terms of appropriate measures, it would be quite useful. Let us try to do this.
A Game
Appu and Tippu play a game. Appu has drawn a triangle ABC (Fig 7.8) and has noted the length of each of its sides and measure of each of its angles.
Tippu has not seen it. Appu challenges Tippu if he can draw a copy of his ∆ABC based on bits of information that Appu would give.
Tippu attempts to draw a triangle congruent to ∆ABC, using the information provided by Appu. The game starts. Carefully observe their conversation and their games.
SSS Game
Appu : One side of ∆ABC is 5.5 cm. Tippu: With this information, I can draw any number of triangles (Fig 7.9) but they need not be copies of ∆ABC.
The triangle I draw may be obtuse-angled or right-angled or acute-angled.
| Author | NCERT |
| Language | English |
| No. of Pages | 20 |
| PDF Size | 1669 KB |
| Category | Education |
| Source/ Credits | ncert.nic.in |
NCERT Solutions Class 7 Maths Chapter 3 Congruence of Triangles
Q1. Complete the following statements:
a) Two-line segments are congruent if.
b) Among two congruent angles, one has a measure of 70°; the measure of another angle is.
c) When we write ∠A = ∠B, we actually mean _.
Solution
a) they have same length.
b) 70°.
c) m ∠A = m ∠B. (m stands for a measure of the angle)
NCERT Class 7 Maths Textbook Chapter 7 With Answer PDF Free Download