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In the figure (i) given below, ABCD is a cyclic quadrilateral. If ∠ADC = 80° and ∠ACD = 52°, find the values of ∠ABC and ∠CBD.

In the figure (i) given below, ABCD is a cyclic quadrilateral. If ∠ADC = 80° and ∠ACD = 52°, find the values of ∠ABC and ∠CBD. Circles, ML Aggarwal Understanding Mathematics Solutions ICSE Class 10.

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Answer

In the given figure,

ABCD is a cyclic quadrilateral.

Since, sum of opposite angles of a cyclic quadrilateral is 180°.

⇒ ∠ABC + ∠ADC = 180°
⇒ ∠ABC + 80° = 180°
⇒ ∠ABC = 180° - 80°
⇒ ∠ABC = 100°.

From figure,

∠DBA = ∠DCA = 52°. (∵ angles in same segment are equal.)

⇒ ∠ABC = ∠DBA + ∠CBD
⇒ 100° = 52° + ∠CBD
⇒ ∠CBD = 100° - 52°
⇒ ∠CBD = 48°.

Hence, ∠ABC = 100° and ∠CBD = 48°.

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