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In the adjoining figure, PQR is a tangent at Q to a circle. If AB is a chord parallel to PR and ∠BQR = 70°, then ∠AQB is equal to

  1. 20°

  2. 40°

  3. 35°

  4. 45°

In the adjoining figure, PQR is a tangent at Q to a circle. If AB is a chord parallel to PR and ∠BQR = 70°, then ∠AQB is equal to (a) 20° (b) 40° (c) 35° (d) 45°. Circles, ML Aggarwal Understanding Mathematics Solutions ICSE Class 10.

Circles

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Answer

From figure,

BQ is chord and PQR is a tangent.

∠BQR = ∠A (∵ angles in alternate segment are equal.)

As AB || PQR

∠BQR = ∠B (∵ alternate angles are equal)

∴ ∠A = ∠B = 70°

We know that sum of angles in a triangle = 180°.

In △AQB,

⇒ ∠A + ∠B + ∠AQB = 180°
⇒ 70° + 70° + ∠AQB = 180°
⇒ 140° + ∠AQB = 180°
⇒ ∠AQB = 180° - 140°
⇒ ∠AQB = 40°.

Hence, Option 2 is the correct option.

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