In the figure given below, ACDE is a cyclic quadrilateral and PAB || EC. If ∠BAC = 35° and ∠DCE = 25°, then what is the value of ∠DEC?

In the figure given below, ACDE is a cyclic quadrilateral and PAB || EC. If ∠BAC = 35° and ∠DCE = 25°, then what is the value of ∠DEC? Correct Answer 85°

GIVEN:

PAB || EC

∠BAC = 35° and ∠DCE = 25°

CONCEPT:

Alternate angles are always equal.

CALCULATION:

∠ACE = ∠BAC = 35°

∠AEC + ∠ACE + ∠EAC = 180°

⇒ 35° + 35°+ ∠EAC = 180°

⇒ ∠EAC = 110°

⇒ ∠EDC = 180° – 110° = 70°

In ∆EDC:

∠EDC + ∠ECD + ∠DEC = 180°

70° + 25°+ ∠DEC = 180°

∴ ∠DEC = 85°

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