Class 7 Maths

Symmetry

Introduction

  • The line about which a figure can be folded to have two congruent parts is called the line of symmetry of that figure.
  • Polygons with equal sides and equal angles are called regular polygons. Regular polygons have more than one line of symmetry. A regular polygon has as many lines of symmetry as the number of sides in it.
  • If an object looks exactly the same after a rotation, it is said that the object has a rotational symmetry.
  • A complete turn is of 360°. The number of times an object looks exactly the same in a complete turn is called the order of rotational symmetry of that object. For example; the order of symmetry of a square is 4.

Exercise 14.2

Question 1: Copy the figures with punched holes and find the axes of symmetry for the following:

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line symmetry figureAnswer:line symmetry figureline symmetry figureAnswer:line symmetry figure


Question 2: Given the line(s) of symmetry, find the other hole(s):

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Question 3: In the following figures, the mirror line (i.e., the line of symmetry) is given as a dotted line. Complete each figure performing reflection in the dotted (mirror) line. (You might perhaps place a mirror along the dotted line and look into the mirror for the image). Are you able to recall the name of the figure you complete?

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