Ex 12.3

Chapter 12 Class 7 Symmetry
Serial order wise

### Transcript

Ex 12.3, 4 Fill in the blanks: (Done before) Square (Done before) Rectangle Rhombus If rotated by 90° This figure is not same as initial figure If rotated by 180° This figure looks same as initial figure Again rotated by 180° Thus, in 1 full – turn (i.e 360°) The figure is same as that of initial 2 turns So, we say that this figure has rotational symmetry of order 2 Regular Hexagon If rotated by 60° Again rotate it by 60° Here, Angle at center = (360°)/6 = 60° Thus, Circle If it rotates 180° It looks same as initial figure If it rotates 90° It looks same as initial figure If it rotates 45° It looks same as initial figure If it rotates 10° It looks same as initial figure If it rotates 0.1° It looks same as initial figure If it rotates 0.01° It looks same as initial figure Therefore, Circle has infinite order of rotational symmetry Semi-Circle If it rotates 90° It is not same as initial figure If it rotates by 180° This is not same as initial figure If it rotates by 360° This is same as initial figure So, this figure on rotation is same as initial figure only when it has rotated 360° So, it has order of rotational symmetry 1

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#### Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.