A cyclic quadrilateral ABCD is such that AB = BC, AD = DC, AC is perpendicular to BD and ∠CAD = θ, then find the ∠ABC. A. θ B. θ/2 C. 2θ D. 3θ
A cyclic quadrilateral ABCD is such that AB = BC, AD = DC, AC is perpendicular to BD and ∠CAD = θ, then find the ∠ABC.
Answer: Option C
∠B + ∠D = 180°
∠A + ∠C = 180°
∠BAC = ∠BCA ∠DAC = ∠DCA
∴∠DAB = ∠DCB = 90°
∠DAC = θ
∴∠ADE = 90° - θ = ∠CDE
∴ ∠ABC = 180° – 2(90° - θ) = 2θ
- θ
- θ/2
- 2θ
- 3θ
Answer & Explanation
Answer: Option C∠B + ∠D = 180°
∠A + ∠C = 180°
∠BAC = ∠BCA ∠DAC = ∠DCA
∴∠DAB = ∠DCB = 90°
∠DAC = θ
∴∠ADE = 90° - θ = ∠CDE
∴ ∠ABC = 180° – 2(90° - θ) = 2θ
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