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Angle OAB=30°and angle OCB=57. FIND ANGLE …

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Angle OAB=30°and angle OCB=57. FIND ANGLE ABC
  • 2 answers

Yogita Ingle 4 years, 2 months ago


Since, OC = OB (Radii of the same circle)
∴  ∠OBC = ∠OCB
⇒  ∠OBC = 57°
In △OBC, we have
 ∠OBC + ∠BOC + ∠OCB = 180°
  57° + ∠BOC + 57° = 180°
⇒  ∠BOC = 66°
In △OAB,we have 
∠OAB + ∠OBA + ∠AOB = 180°   (Since, AO=OB  ∴ ∠OAB = ∠OBA)
 30° + 30° + ∠AOB = 180°
⇒  ∠AOB = 180° – 60°
⇒  ∠AOB = 120°
     ∠ABC = 180 - ∠AOB - ∠OAB
                = 180- ( 120° + 30)°
= 30°

Gaurav Seth 4 years, 2 months ago

Solution  :-

Since, OC = OB (Radii of the same circle)
∴  ∠OBC = ∠OCB
⇒  ∠OBC = 57°
In △OBC, we have
 ∠OBC + ∠BOC + ∠OCB = 180°
  57° + ∠BOC + 57° = 180°
⇒  ∠BOC = 66°
In △OAB,we have 
∠OAB + ∠OBA + ∠AOB = 180°   (Since, AO=OB  ∴ ∠OAB = ∠OBA)
 30° + 30° + ∠AOB = 180°
⇒  ∠AOB = 180° – 60°
⇒  ∠AOB = 120°
     ∠AOC = ∠AOB - ∠BOC
                = 120° – 66° = 54°

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