∵ABCD是正方形,∴AC?BD.∵CE?面ABCD,∴CE?BD. 又AC?CE?C,∴BD?面ACE. ∵AE?面ACE,∴BD?AE, ∴B1D1?AE.
(Ⅱ)证明:作BB1的中点F,连结AF、CF、EF. ∵E、F是CC1、BB1的中点,∴CEB1F,
∴四边形B1FCE是平行四边形,∴ CF// B1E. ∵E,F是CC1、BB1的中点,∴EF//BC, 又BC//AD,∴EF//AD.
∴四边形ADEF是平行四边形,?AF//ED, ∵AF?CF?C,B1E?ED?E, ∴平面ACF//面B1DE.
又AC?平面ACF,∴AC//面B1DE. (3)S ?ABD?12AB?AD?2.VA?BDE?V?EAB?1D3S? A?BCE?1D3S?2
?ABCDE?.3
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