求cos a的值 (必修四数学)已知0<a<兀/3,cos(a+兀/6)=3/5,sin(a+兀/6)=4/5答案说cos a=(3根号3+4)/10
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![求cos a的值 (必修四数学)已知0<a<兀/3,cos(a+兀/6)=3/5,sin(a+兀/6)=4/5答案说cos a=(3根号3+4)/10](/uploads/image/z/14399265-57-5.jpg?t=%E6%B1%82cos+a%E7%9A%84%E5%80%BC+%28%E5%BF%85%E4%BF%AE%E5%9B%9B%E6%95%B0%E5%AD%A6%EF%BC%89%E5%B7%B2%E7%9F%A50%EF%BC%9Ca%EF%BC%9C%E5%85%80%2F3%2Ccos%28a%2B%E5%85%80%2F6%EF%BC%89%3D3%2F5%2Csin%28a%2B%E5%85%80%2F6%29%3D4%2F5%E7%AD%94%E6%A1%88%E8%AF%B4cos+a%3D%EF%BC%883%E6%A0%B9%E5%8F%B73%2B4%EF%BC%89%2F10)
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