If from a external point P of a circle with centre O, two tangents PQ and PRare drawn such that angle of QPR=120. prove tht 2PQ=PO.
Here is the answer to your query.
Given : BC and BD are tangents with ∠DBC = 120°
(tangent from an external point are equally inclined to the segment joining the centre to that point)
Now in ΔBCO
⇒ OB = 2BC = BC + BC
⇒ OB = BC + BD ( BC = BD as tangents drawn from an external point to a circle are equal)