在三角形ABC中,AB=2,cosC=2*根号7/7,点D是AC边上一点,满座AD=2DC,且cos∠DBC=(5根号7)/14.1求角BDC大小,2小问是向量AD点乘向量CB.
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![在三角形ABC中,AB=2,cosC=2*根号7/7,点D是AC边上一点,满座AD=2DC,且cos∠DBC=(5根号7)/14.1求角BDC大小,2小问是向量AD点乘向量CB.](/uploads/image/z/1693317-21-7.jpg?t=%E5%9C%A8%E4%B8%89%E8%A7%92%E5%BD%A2ABC%E4%B8%AD%2CAB%3D2%2CcosC%3D2%2A%E6%A0%B9%E5%8F%B77%2F7%2C%E7%82%B9D%E6%98%AFAC%E8%BE%B9%E4%B8%8A%E4%B8%80%E7%82%B9%2C%E6%BB%A1%E5%BA%A7AD%3D2DC%2C%E4%B8%94cos%E2%88%A0DBC%3D%EF%BC%885%E6%A0%B9%E5%8F%B77%EF%BC%89%2F14.1%E6%B1%82%E8%A7%92BDC%E5%A4%A7%E5%B0%8F%2C2%E5%B0%8F%E9%97%AE%E6%98%AF%E5%90%91%E9%87%8FAD%E7%82%B9%E4%B9%98%E5%90%91%E9%87%8FCB.)
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