1. If in the given figure, \(O\) is the point of intersection of two chords \(CD\) and \(EF\) such that \(OD\) \(= \)\(OF\), then triangles \(OCE\) and \(OFD\) are
2. \(D\) and \(E\) are respectively the points on the sides \(AB\) and \(AC\) of a triangle \(ABC\) such that \(AD =\)11\(cm\), \(BD =\)5\(cm\), \(BC = \)8\(cm\) and \(DE||BC\). Then, length of \(DE\) (in \(cm\)) is