3.在正方体ABCD−A1B1C1D1ABCD-A_{1}B_{1}C_{1}D_{1}ABCD−A1B1C1D1中,EEE,FFF分别为ABABAB,ADADAD的中点,则异面直线D1CD_{1}CD1C与EFEFEF所成角的大小为((( )))