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In the given figure, ∠ADC = 130° and BC = BE. Find ∠CBE if AB ⊥ CE.

In the given figure, ∠ADC = 130° and BC = BE. Find ∠CBE if AB ⊥ CE. Chapterwise Revision, Concise Mathematics Solutions ICSE Class 10.

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Answer

Since, ABCD is a cyclic quadrilateral and sum of opposite angles in a cyclic quadrilateral = 180°.

∴ ∠ADC + ∠ABC = 180°

⇒ 130° + ∠ABC = 180°

⇒ ∠ABC = 50°.

In the given figure, ∠ADC = 130° and BC = BE. Find ∠CBE if AB ⊥ CE. Chapterwise Revision, Concise Mathematics Solutions ICSE Class 10.

From figure,

⇒ ∠FBC = ∠ABC = 50°.

In △FBC,

By angle sum property of triangle,

⇒ ∠FBC + ∠BCF + ∠CFB = 180°

⇒ 50° + ∠BCF + 90° = 180°

⇒ ∠BCF = 180° - 90° - 50° = 40°.

Given,

BC = BE

In △BCE,

⇒ ∠BEC = ∠BCE = 40°. (As angles opposite to equal sides are equal)

In △FBE,

By angle sum property of triangle,

⇒ ∠BEF + ∠FBE + ∠EFB = 180°

⇒ 40° + ∠FBE + 90° = 180°

⇒ ∠FBE = 180° - 90° - 40° = 50°.

From figure,

∠CBE = ∠FBC + ∠FBE = 50° + 50° = 100°.

Hence, ∠CBE = 100°.

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