4. TBQ - Circles and tangents

 

In the figure, \(CP\) and \(CQ\) are tangents to the circle with the centre at \(O\). \(ARB\) is another tangent touching the circle at \(R\). If \(CP = 13\) \(cm\) and \(BC = 5\) \(cm\), then the length of \(BR\) is: