来自贾宝才的问题
(2013•浙江模拟)已知直角梯形ABCD中,AD⊥DC,AD⊥AB,△CDE是边长为2的等边三角形,AB=5.沿CE将△BCE折起,使B至B′处,且B′C⊥DE;然后再将△ADE沿DE折起,使A至A′处,且面A′DE⊥面CDE,
(2013•浙江模拟)已知直角梯形ABCD中,AD⊥DC,AD⊥AB,△CDE是边长为2的等边三角形,AB=5.沿CE将△BCE折起,使B至B′处,且B′C⊥DE;然后再将△ADE沿DE折起,使A至A′处,且面A′DE⊥面CDE,△B′CE和△A′DE在面CDE的同侧.
(Ⅰ) 求证:B′C⊥平面CDE;
(Ⅱ) 求平面B′A′D与平面CDE所构成的锐二面角的余弦值.
1回答
2020-12-1306:42