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The given figure shows a circle with center O and ∠ABP = 42°. Calculate the measure of :

(i) ∠PQB

(ii) ∠QPB + ∠PBQ

The given figure shows a circle with center O and ∠ABP = 42°. Calculate the measure of : ∠PQB ∠QPB + ∠PBQ. Hence, show that AC is a diameter. Circles, Concise Mathematics Solutions ICSE Class 10.

Circles

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The given figure shows a circle with center O and ∠ABP = 42°. Calculate the measure of : ∠PQB ∠QPB + ∠PBQ. Hence, show that AC is a diameter. Circles, Concise Mathematics Solutions ICSE Class 10.

(i) We know that,

Angle in a semi-circle is a right angle.

∠APB = 90°.

In △APB,

⇒ ∠APB + ∠ABP + ∠BAP = 180° [Angle sum property of triangle]

⇒ 90° + 42° + ∠BAP = 180°

⇒ ∠BAP + 132° = 180°

⇒ ∠BAP = 180° - 132° = 48°.

From figure,

∠PQB = ∠BAP = 48° [Angles in same segment are equal]

Hence, ∠PQB = 48°.

(ii) In △BQP,

⇒ ∠QPB + ∠PBQ + ∠PQB = 180° [Angle sum property of triangle]

⇒ ∠QPB + ∠PBQ + 48° = 180°

⇒ ∠QPB + ∠PBQ = 180° - 48°

⇒ ∠QPB + ∠PBQ = 132°.

Hence, ∠QPB + ∠PBQ = 132°.

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