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In the given figure, ∠ACE = 43° and ∠CAF = 62°; find the values of a, b and c.

In the given figure, ∠ACE = 43° and ∠CAF = 62°; find the values of a, b and c. Circles, Concise Mathematics Solutions ICSE Class 10.

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Answer

In △AEC,

⇒ ∠ACE + ∠CAE + ∠AEC = 180°

⇒ 43° + 62° + ∠AEC = 180°

⇒ ∠AEC = 180° - 105° = 75°.

From figure,

⇒ ∠ABD + ∠AED = 180° [As sum of opposite angles in a cyclic quadrilateral = 180°]

⇒ a + ∠AEC = 180° [From figure, ∠AED = ∠AEC]

⇒ a + 75° = 180°

⇒ a = 180° - 75° = 105°.

∠BDC = c [Vertically opposite angles are equal]

∠DBC = 180° - a [Linear pairs]
= 180° - 105°
= 75°.

In △DBC,

⇒ ∠DBC + ∠BCD + ∠BDC = 180° [Angle sum property of triangle]

⇒ 75° + 43° + c = 180°

⇒ 118° + c = 180°

⇒ c = 180° - 118° = 62°.

In △BAF,

⇒ ∠ABF + ∠BAF + ∠AFB = 180° [Angle sum property of triangle]

⇒ a + 62° + b = 180°

⇒ 105° + 62° + b = 180°

⇒ b + 167° = 180°

⇒ b = 180° - 167° = 13°.

Hence, a = 105°, b = 13° and c = 62°.

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