Question : If the given figure, lines AB and cd intersect at point o. If ∠AOD = 58° , Find ∠BOC


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Ex 1: - If ∠AOC = 120°, find ∠BOD


Explanation: ∠AOC and ∠BOD are vertically opposite ∠BOD = 120∘ : বিপৰীত কোণ ⇒ সমান ⇒ ∠BOD = 120°


Ex 2:-  If ∠AOD = 75°, find ∠BOC


Explanation: These are vertically opposite ∠BOC = 75∘ 


Ex 3 : If ∠AOD = 50°, find ∠AOC


Explanation:



  • ∠AOD and ∠AOC form a linear pair

  • Linear pair sum = 180°


∠AOC = 180∘ − 50∘ = 130∘ (Linear pair ⇒ যোগফল 180° ∠AOC = 130°)


Revision (পুনৰালোচনা)



  • Vertically opposite angles = Equal (সমান)

  • Linear pair angles = 180° (যোগফল 180°)

  • Intersecting lines → always form 4 angles