Symmetry class 7 notes i.e. for chapter 14 provided here are concise, simple and easily understandable. These notes will not only help class 7 students to learn this chapter in a more effective way but will also help them to revise the topics easily. This chapter 14 notes include the following key points-
- Meaning of Symmetry
- Types of Symmetry
- Important Terms Related to Symmetry
- Examples
- Practice Questions
- Symmetry Related Articles
Meaning of Symmetry
Symmetry is when two or more parts remain identical after a turn, slide, or flip. Examples of symmetry includes mirror reflections, folding a rectangular paper exactly from the middle, etc. There are two main types of symmetry which are discussed in detail below.
Types of Symmetry
There are several types of symmetry which are reflective or line symmetry, rotational symmetry, point symmetry, translational symmetry, helical, glide reflectional, etc. Among these types, two are considered the most important and are explained in detail in the following articles-
Important Terms Related to Symmetry
- Line of Symmetry:
It is a line about which the figure may be folded so that the two parts of the figure will coincide. For regular polygons, there are multiple lines of symmetry. The number of lines of symmetry for a few common polygons are mentioned below.
Type of Regular Polygon |
Number of Lines of Symmetry |
Equilateral Triangle |
3 |
Square |
4 |
Regular Pentagon |
5 |
Regular Hexagon |
6 |
- Centre and Angle of Rotation
The centre of rotation is that fixed point from which an object is rotated. Also, the angle of rotation is that angle by which an object rotates. The rotation of an object from its centre of rotation can be either clockwise or anticlockwise and angle can be up to 360 degrees which means object is rotated completely.
- Order of Rotational Symmetry
Order of rotational symmetry is the number of times an object looks exactly the same after a complete turn. For example, the order of symmetry for a square is 4 while for an equilateral triangle, it is 3.
Example Questions
Question 1:
Give three examples of any shapes which have no line of symmetry.
Solution:
Scalene triangle, quadrilateral, and parallelograms are three examples of shapes which have no line of symmetry.
Question 2:
Practice Questions
- Give example of any two figures which have both rotational and line symmetry.
- How many lines of symmetry does the following figures have – (i) A rhombus, (ii) A scalene triangle, and (iii) circle
- If a figure has two or more lines of symmetry, should it have rotational symmetry of
order more than 1?
Symmetry Related Articles
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