8. 如图,平行六面体ABCD−A1B1C1D1ABCD-A_{1}B_{1}C_{1}D_{1}ABCD−A1B1C1D1的各棱长均为1,∠A1AB=∠A1AD=60∘\angle A_{1}AB=\angle A_{1}AD=60\circ∠A1AB=∠A1AD=60∘,∠DAB=90∘\angle DAB=90\circ∠DAB=90∘,则∣AC1→∣=(\vert {\overrightarrow{A{C_1}}}\vert =(∣AC1∣=( )))