1. \(AD\) is a diameter of a circle and \(AB\) is a chord. If \(AD = 34 cm\), \(AB = 30 cm\), the distance of \(AB\) from the centre of the circle is :
2. In the figure, if \(OA = 5 cm\), \(AB = 8 cm\) and \(OD\) is perpendicular to \(AB\), then \(CD\) is equal to: