Ex 14.2, 2 (b) - Chapter 14 Class 7 Symmetry

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Ex 14.2, 2 (b) Give the order of rotational symmetry for each figure: Here, ∠AOB = 80° But, ∠AOB + ∠BOC = 180° 80° + ∠BOC = 180° ∠BOC = 180° − 80° ∠BOC = 100° Also, ∠AOB = ∠COD = 80° And ∠BOC = ∠ AOD = 100° Given (Linear pair) (Vertically opposite Angles) If rotated by 80° This figure doesn’t look same as previous If rotated by 90° This figure doesn’t look same as previous If rotated by 180° This figure looks same as previous Again rotated by 180° This figure looks same as previous Thus, Thus, in 1 full turn (i.e. 360°) This figure is same as that of initial 2 turns So, we say that this figure has rotational symmetry of order 2