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Ex 7.2, 8 - Show that angles of equilateral triangle are 60 - Ex 7.2

  1. Chapter 7 Class 9 Triangles
  2. Serial order wise
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Ex7.2, 8 Show that the angles of an equilateral triangle are 60° each. Given: ∆ABC be an equilateral triangle. ∴ AB = BC = AC To prove: ∠A = ∠B = ∠C = 60° Proof: AB = AC ⇒ ∠C = ∠B Also, AC = BC ⇒ ∠B = ∠A From (1) & (2) ∠A = ∠B = ∠C In ΔABC, ∠A + ∠B + ∠C = 180° ⇒ ∠A + ∠A + ∠A = 180° ⇒ 3∠A = 180° ⇒ ∠A ⇒ ∠A ∴ ∠A = ∠B = ∠C = 60° Hence proved

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