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Assertion (A) : In the figure below, O is the center of the circle and ∠AOC = 160°. Then x = 100° and y = 80°.

Assertion (A) : In the figure below, O is the center of the circle and ∠AOC = 160°. Then x = 100° and y = 80°. Reason (R) : The angle, which an arc of a circle subtends at the centre of the circle is double that which it subtends at any point on the remaining part of the circumference. Assertion-Reasoning Type Questions, Concise Mathematics Solutions ICSE Class 10.

Reason (R) : The angle, which an arc of a circle subtends at the centre of the circle is double that which it subtends at any point on the remaining part of the circumference.

  1. A is true, R is false.

  2. A is false, R is true.

  3. Both A and R are true.

  4. Both A and R are false.

Circles

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Answer

We know that,

The angle, which an arc of a circle subtends at the centre of the circle is double that which it subtends at any point on the remaining part of the circumference.

From figure,

⇒ 2x = ∠AOC

⇒ 2x = 160°

⇒ x = 160°2\dfrac{160°}{2} = 80°.

We know that,

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

⇒ x + y = 180°

⇒ 80° + y = 180°

⇒ y = 180° - 80° = 100°.

∴ Assertion (A) is false and Reason (R) is true.

Hence, Option 2 is the correct option.

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