In a circle, chord AB and CD meet a point P outside the circle and chord AC and BD meet a point Q outside the circle. If ∠ACD = 70° and ∠CAB = 40°, then, what is the value of (∠APC - ∠BQA)?
In a circle, chord AB and CD meet a point P outside the circle and chord AC and BD meet a point Q outside the circle. If ∠ACD = 70° and ∠CAB = 40°, then, what is the value of (∠APC - ∠BQA)? Correct Answer 40°
Given:
∠ACD = 70° and ∠CAB = 40°
Calculation:
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We know that, ∠CAB + ∠CDB = 180°
⇒ 40° + ∠CDB = 180°
⇒ ∠CDB = 140°
Thus, ∠PDB = 180° - 140° = 40°
Similarly, ∠PBD = 70°
In ΔBPD –
∠PBD + ∠PDB + ∠BPD = 180°
⇒ 70° + 40° + ∠BPD = 180°
⇒ ∠BPD = 180° - 110°
⇒ ∠BPD = ∠APC = 70° ---- (1)
In ΔCDQ –
∠CDQ + ∠DCQ + ∠DQC = 180°
⇒ 40° + (180° - 70°) + ∠DQC = 180°
⇒ ∠DQC = ∠BQA = 30° ---- (2)
According to question -
∴ ∠APC - ∠BQA = 70° - 30° = 40°