Ken's Timetable
Monday
Tuesday
Wednesday
Thursday
Friday
9:10 a.m.
Math
English
10:20 a.m.
P.E.
History
Science
Biology
11:15 a.m.
Chinese
2:00 p.m.
3:00 p.m.
(Ⅰ)证明:CD⊥平面PAD;
(Ⅱ)若二面角P﹣CD﹣A的大小为45°,求几何体C﹣PBE的体积.
北魏太武帝与南朝交战,其战书上写道:“吾今所遣斗兵,尽非我国(鲜卑)人。城东北是丁零与胡,南是氐、羌。设使丁零死,正可减常山、赵郡贼;胡死,减并州贼;氐、羌死,减关中贼。”这不能说明( )