【急】已知向量a=(cos3x/2,sin3x/2),向量b=(cosx/2,-sinx/2),x∈[-∏/3,∏/2](1)求证(a-b)⊥(a+b)(2)若|a+b|=1/3,求cosx的值
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![【急】已知向量a=(cos3x/2,sin3x/2),向量b=(cosx/2,-sinx/2),x∈[-∏/3,∏/2](1)求证(a-b)⊥(a+b)(2)若|a+b|=1/3,求cosx的值](/uploads/image/z/616522-58-2.jpg?t=%E3%80%90%E6%80%A5%E3%80%91%E5%B7%B2%E7%9F%A5%E5%90%91%E9%87%8Fa%3D%28cos3x%2F2%2Csin3x%2F2%29%2C%E5%90%91%E9%87%8Fb%3D%28cosx%2F2%2C-sinx%2F2%29%2Cx%E2%88%88%5B%EF%BC%8D%E2%88%8F%2F3%2C%E2%88%8F%2F2%5D%281%29%E6%B1%82%E8%AF%81%EF%BC%88a-b%EF%BC%89%E2%8A%A5%EF%BC%88a%2Bb%EF%BC%89%282%29%E8%8B%A5%7Ca%2Bb%7C%3D1%2F3%2C%E6%B1%82cosx%E7%9A%84%E5%80%BC)
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