Given Two tangents PQ and PR are drawn from an external point to a circle with centre O.
To prove QORP is a cyclic quadrilateral.
proof Since, PR and PQ are tangents.
So, `ORbotPRand OQbotPQ`
[since, if we drawn a line from centre of a circle to its tangent line. Then the line always perpendicular to the tangent line]
`:.angleORP=angleOQP=90^(@)`
Hence, `angleORP+angleOQP=180^(@)`
So, QOPR is cyclic quadrilateral.
[If sum of opposite angles is quadrilateral in `180^(@)` then the quadrilateral is cyclic]
