13. 如图,已知正四棱柱ABCD−A1B1C1D1ABCD-A_{1}B_{1}C_{1}D_{1}ABCD−A1B1C1D1,底面正方形ABCDABCDABCD的边长为2,AA1=3AA_{1}=3AA1=3.(1)求证:平面AA1CC1⊥AA_{1}CC_{1}\botAA1CC1⊥平面A1BDA_{1}BDA1BD;(2)求点AAA到平面A1BDA_{1}BDA1BD的距离.