Two equal tangents PQ and PR are drawn from an external point P on a circle with centre O. if PO = 16√3m and the angle between the tangents is 60°. What is the length of each tangent and find the value of ∠QSR.
Two equal tangents PQ and PR are drawn from an external point P on a circle with centre O. if PO = 16√3m and the angle between the tangents is 60°. What is the length of each tangent and find the value of ∠QSR. Correct Answer 24m, 60°
Given:
PO = 16√3m
The angle between the tangents = 60°
Calculation:
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⇒ ∠QPO = ∠RPO
⇒ ∠QPO = ½ × ∠QPR = ½ × 60°
⇒ ∠QPO = 30°
In a Δ QPO,
⇒ ∠PQO = 90° (∵ PQ is a tangent)
⇒ cos 30° = PQ/PO
⇒ √3/2 = PQ/16√3
⇒ PQ = 24 m
⇒ PQ = PR = 24m
In a quadrilateral PQOR,
⇒ ∠PQO + ∠QOR + ∠ORP + ∠RPQ = 360°
⇒ 90° + ∠QOR + 90° + 60° = 360°
⇒ ∠QOR = 120°
⇒ ∠QOR = 2∠QSR (Same chord QR)
⇒ ∠QSR = 60°
∴ The length of each tangent is 24m and the value of ∠QSR is 60°.