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如图所示 正三棱柱a1b1c1 如图所示,正三棱柱ABC-A
如图所示,正三棱柱ABC-A (Ⅰ)证明:设AB1与A1B相交于点P,连接PD,则P为AB1中点,∵D为AC中点,∴PD∥B1C.又∵PD?平面A1BD,∴B1C∥平面A1BD.(4分)(Ⅱ)解法一:由正三棱柱ABC-A1B1C1中D是AC...
如图所示,正三棱柱ABC-A (Ⅰ)证明:设AB1与A1B相交于点P,连接PD,则P为AB1中点,∵D为AC中点,∴PD∥B1C.又∵PD?平面A1BD,∴B1C∥平面A1BD.(4分)(Ⅱ)解法一:由正三棱柱ABC-A1B1C1中D是AC...