1 Theorem 6.1 - If two lines intersect each other .jpg

2 Theorem 6.1 - Vertically Opposite Angles are equal.jpg

  1. Chapter 6 Class 9 Lines and Angles
  2. Serial order wise
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Theorem 6.1 :- If two lines intersect each other, then the vertically opposite angles are equal. Given :- Two lines AB and CD intersecting at point O. To Prove :- Vertically opposite angles are equal i.e, ∠AOC =∠BOD and ∠AOD=∠BOC Proof :- From (1) and (2) ∠AOC + ∠BOC = ∠AOD + ∠AOC ⇒∠BOC = ∠AOD Now, To prove ∠BOD = ∠AOC From (3) and (4) ∠AOD + ∠BOD = ∠AOD + ∠AOC ∠BOD = ∠AOC Hence, Vertically Opposite angles are equal.

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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.