Page 251 - Math_Genius_V1.0_C7_Flipbook
P. 251
D:\Surender Prajapati\CBSE_ICSE_Book_New\CBSE\Grade-7\Math_Genius-7\Open_File\11_Chapter\11_Chapter
\ 15-Nov-2024 Surender Prajapati Proof-6 Reader’s Sign _______________________ Date __________
Example 5: Find the order of rotational symmetry for the following figure:
O 180° O
Solution: Here, angle of rotation of the image is 180°.
360°
So, the order of rotational symmetry = = 2
180°
Thus, the shape will fit onto itself two times in a complete rotation.
Think and Answer
What is the order of rotational symmetry for the following figures?
(a) (b) (c)
Line of Symmetry and Rotational Symmetry
Some shapes have both line of symmetry and rotational symmetry.
For example, a square has 4 lines of symmetry and has rotational symmetry of order 4, as shown
below.
P P P
90° 90°
90° 90°
P P
(i) (ii) (iii) (iv) (v)
Line Symmetry Rotational symmetry of order 4
Similarly, a rectangle, equilateral triangle, regular pentagon, circle, etc. are some more geometrical
figures which have both line symmetry and rotational symmetry.
Look at the table of some geometrical figures which have line symmetry as well as rotational
symmetry.
Geometrical Figures Reflection Symmetry Rotational Symmetry
l 1
l 2
l 3
l 4
Square Four lines of symmetry Order 4
l 1
l 2
Rectangle Two lines of symmetry Order 2
249 Symmetry
