一、已知正方体ABCD—A1B1C1D1中,E、F分别是D1D、BD的中点,G在棱CD上,且CG=1/3GD,H为C1G中点1、求证:EF⊥B1C;2、求EF与C1G所成角的余弦值;3、求FH的长二、棱长为a的正方体ABCD-A1B1C1D1中,在棱DD1上是
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![一、已知正方体ABCD—A1B1C1D1中,E、F分别是D1D、BD的中点,G在棱CD上,且CG=1/3GD,H为C1G中点1、求证:EF⊥B1C;2、求EF与C1G所成角的余弦值;3、求FH的长二、棱长为a的正方体ABCD-A1B1C1D1中,在棱DD1上是](/uploads/image/z/1581235-43-5.jpg?t=%E4%B8%80%E3%80%81%E5%B7%B2%E7%9F%A5%E6%AD%A3%E6%96%B9%E4%BD%93ABCD%E2%80%94A1B1C1D1%E4%B8%AD%2CE%E3%80%81F%E5%88%86%E5%88%AB%E6%98%AFD1D%E3%80%81BD%E7%9A%84%E4%B8%AD%E7%82%B9%2CG%E5%9C%A8%E6%A3%B1CD%E4%B8%8A%2C%E4%B8%94CG%3D1%2F3GD%2CH%E4%B8%BAC1G%E4%B8%AD%E7%82%B91%E3%80%81%E6%B1%82%E8%AF%81%EF%BC%9AEF%E2%8A%A5B1C%EF%BC%9B2%E3%80%81%E6%B1%82EF%E4%B8%8EC1G%E6%89%80%E6%88%90%E8%A7%92%E7%9A%84%E4%BD%99%E5%BC%A6%E5%80%BC%EF%BC%9B3%E3%80%81%E6%B1%82FH%E7%9A%84%E9%95%BF%E4%BA%8C%E3%80%81%E6%A3%B1%E9%95%BF%E4%B8%BAa%E7%9A%84%E6%AD%A3%E6%96%B9%E4%BD%93ABCD-A1B1C1D1%E4%B8%AD%2C%E5%9C%A8%E6%A3%B1DD1%E4%B8%8A%E6%98%AF)
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