PQ is tangent to circle and OP is radius
⇒ ∠OPQ= 90° …radius is perpendicular to tangent
⇒ ∠PQO = 30° …given
Consider ΔOPQ
⇒ ∠OPQ + ∠PQO + ∠POQ = 180° …sum of angles of triangle
⇒ 90° + 30° + ∠POQ = 180°
⇒ 120° + ∠POQ = 180°
⇒ ∠POQ = 60°
Hence ∠POQ is 60°