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In the figure (i) given below, triangle ABC is equilateral. Find ∠BDC and ∠BEC.

In the figure (i) given below, triangle ABC is equilateral. Find  ∠BDC and ∠BEC. Circles, ML Aggarwal Understanding Mathematics Solutions ICSE Class 10.

Circles

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Answer

Since ABC is an equilateral triangle so,

∠A = ∠B = ∠C = 60°.

From figure,

∠BDC = ∠BAC (∵ angles in alternate segments are equal.)

∴ ∠BDC = 60°.

BDCE is a cyclic quadrilateral. Hence, sum of the opposite angles = 180°.

⇒ ∠BDC + ∠BEC = 180°
⇒ 60° + ∠BEC = 180°
⇒ ∠BEC = 180° - 60° = 120°.

Hence, the value of ∠BDC = 60° and ∠BEC = 120°.

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