Mathematics

Use the given figure to find :

(i) ∠BAD

(ii) ∠DQB.

Use the given figure to find ∠BAD ∠DQB. Circles, Concise Mathematics Solutions ICSE Class 10.

Circles

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Answer

(i) In △ADP,

⇒ ∠PAD + ∠ADP + ∠DPA = 180° [Angle sum property of triangle]

⇒ ∠PAD + 85° + 40° = 180°

⇒ ∠PAD + 125° = 180°

⇒ ∠PAD = 180° - 125° = 55°.

From figure,

⇒ ∠BAD = ∠PAD = 55°.

Hence, ∠BAD = 55°.

(ii) We know that,

Sum of opposite angles in a cyclic quadrilateral = 180°.

⇒ ∠ABC + ∠ADC = 180°

⇒ ∠ABC + 85° = 180°

⇒ ∠ABC = 180° - 85° = 95°.

In △AQB,

⇒ ∠AQB + ∠QAB + ∠ABQ = 180° [Angle sum property of triangle]

⇒ ∠AQB + ∠BAD + ∠ABC = 180° [From figure, ∠QAB = ∠BAD and ∠ABQ = ∠ABC]

⇒ ∠AQB + 55° + 95° = 180°

⇒ ∠AQB + 150° = 180°

⇒ ∠AQB = 180° - 150° = 30°.

From figure,

⇒ ∠DQB = ∠AQB = 30°.

Hence, ∠DQB = 30°.

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