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°
মোঃ আরিফুল ইসলাম
Feb 20, 2025