7. 平行六面体ABCD−A1B1C1D1ABCD-A_{1}B_{1}C_{1}D_{1}ABCD−A1B1C1D1的所有棱长都是1，OOO为A1C1A_{1}C_{1}A1C1中点，∠BAD=∠BAA1=∠DAA1=60∘\angle BAD=\angle BAA_{1}=\angle DAA_{1}=60\circ∠BAD=∠BAA1=∠DAA1=60∘，AO→=AA1→+xAB→+yAD→\overrightarrow{AO}=\overrightarrow{A{A}_{1}}+x\overrightarrow{AB}+y\overrightarrow{AD}AO=AA1+xAB+yAD，则((( )))