求“已知sinα=15/17,α∈(π/2,π),求cos(π/3-α)的值”的答案和“已知cosθ=-5/13,α∈(π,3/2π),求cos(θ-π/6)的值”的答案,谢谢额……可以加上过程么谢谢
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![求“已知sinα=15/17,α∈(π/2,π),求cos(π/3-α)的值”的答案和“已知cosθ=-5/13,α∈(π,3/2π),求cos(θ-π/6)的值”的答案,谢谢额……可以加上过程么谢谢](/uploads/image/z/3711063-39-3.jpg?t=%E6%B1%82%E2%80%9C%E5%B7%B2%E7%9F%A5sin%CE%B1%3D15%2F17%2C%CE%B1%E2%88%88%28%CF%80%2F2%2C%CF%80%29%2C%E6%B1%82cos%28%CF%80%2F3-%CE%B1%29%E7%9A%84%E5%80%BC%E2%80%9D%E7%9A%84%E7%AD%94%E6%A1%88%E5%92%8C%E2%80%9C%E5%B7%B2%E7%9F%A5cos%CE%B8%3D-5%2F13%2C%CE%B1%E2%88%88%28%CF%80%2C3%2F2%CF%80%29%2C%E6%B1%82cos%28%CE%B8-%CF%80%2F6%29%E7%9A%84%E5%80%BC%E2%80%9D%E7%9A%84%E7%AD%94%E6%A1%88%2C%E8%B0%A2%E8%B0%A2%E9%A2%9D%E2%80%A6%E2%80%A6%E5%8F%AF%E4%BB%A5%E5%8A%A0%E4%B8%8A%E8%BF%87%E7%A8%8B%E4%B9%88%E8%B0%A2%E8%B0%A2)
求“已知sinα=15/17,α∈(π/2,π),求cos(π/3-α)的值”的答案和“已知cosθ=-5/13,α∈(π,3/2π),求cos(θ-π/6)的值”的答案,谢谢额……可以加上过程么谢谢
求“已知sinα=15/17,α∈(π/2,π),求cos(π/3-α)的值”的答案
和“已知cosθ=-5/13,α∈(π,3/2π),求cos(θ-π/6)的值”的答案,谢谢
额……可以加上过程么谢谢
求“已知sinα=15/17,α∈(π/2,π),求cos(π/3-α)的值”的答案和“已知cosθ=-5/13,α∈(π,3/2π),求cos(θ-π/6)的值”的答案,谢谢额……可以加上过程么谢谢
因为sinα=15/17,α∈(π/2,π),所以cosa<0
所以cosa=-8/17
cos(π/3-α)=cosπ/3cosa+sinπ/3sina=-4/17+15根号3/34=(15根号3-8)/34
因为cosθ=-5/13,α∈(π,3/2π),
sina=-12/13
cos(θ-π/6)=cosacosπ/6+sinasinπ/6=-5根号3/26-12/26=-(5根号3+12)/26
1、(15倍根号3-8)/34
2、-(5倍根号3+12)/26
sinα=15/17,α∈(π/2,π),求cos(π/3-α)的值
cosα=-8/17
cos(π/3-α)=cosπ/3cosα+sinπ/3sinα
=-1/2*(-8/17)+√3/2*15/17
=(8+15√3)/34
cosθ=-5/13,θ∈(π,3/2π),求cos(θ-...
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sinα=15/17,α∈(π/2,π),求cos(π/3-α)的值
cosα=-8/17
cos(π/3-α)=cosπ/3cosα+sinπ/3sinα
=-1/2*(-8/17)+√3/2*15/17
=(8+15√3)/34
cosθ=-5/13,θ∈(π,3/2π),求cos(θ-π/6)的值
sinθ=-12/13
cos(θ-π/6)=cosθcosπ/6+sinθsinπ/6
=-5/13*√3/2-12/13*1/2
=-(5√3+12)/26
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