Class 7 Maths Symmetry Lines of Symmetry For Regular Polygons

Lines of Symmetry For Regular Polygons

The concept of line symmetry is closely related to mirror reflection. A shape has line symmetry when one half of it is the mirror image of the other half. So, a mirror line helps to visualise a line of symmetry.                                                           

If an object has more than one line of symmetry then such figures are said to have multiple lines of symmetry. Each regular polygon like triangle, square, etc. has as many lines of symmetry as it has sides as shown in the given figure.

           Class_7_Maths_Symmetry_DifferentShapes

 Hence, we can say that they have multiple lines of symmetry.

Problem: State the number of lines of symmetry for the following figures:

(a) An equilateral triangle                     (b) An isosceles triangle                   (c) A scalene triangle

(d) A square                                             (e) A rectangle                                    (f) A rhombus       

(g) A parallelogram                                (h) A quadrilateral                              (i) A regular hexagon   

(j) A circle

Solution:

 Class_7_Maths_Symmetry_DifferentShapes1

Class_7_Maths_Symmetry_DifferentShapes2

Problem: What letters of the English alphabet have reflection symmetry (i.e., symmetry related to

mirror reflection) about.

(a) a vertical mirror       (b) a horizontal mirror       (c) both horizontal and vertical mirrors

Answer:

(a) Vertical mirror – A, H, I, M, O, T, U, V, W, X and Y

                     Class_7_Maths_Symmetry_Mirror_Shape                     

(b) Horizontal mirror – B, C, D, E, H, I, O and X

       Class_7_Maths_Symmetry_Horizontal_Mirror_Shape                                

(c) Both horizontal and vertical mirror – H, I, O and X.

 

 

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