A:(﹣∞,2)
B:(1,2)
C:(2,+∞)
D:(1,2)∪(2,+∞)
已知正四棱锥S-ABCD的侧棱长与底面边长都相等,E是SB的中点,则AE,SD所成的角的余弦值为( )
________a teacher has given permission is a student allowed to enter the classroom.
班氏丝虫寄生在人体的淋巴管内后,常造成人体下肢肿胀,这是由于( )