已知α∈(π/2,π)且sin0.5α+cos0.5α=根号6/2.一,求cosα的值(已求出为负的根号3/2)二,sin(α-...已知α∈(π/2,π)且sin0.5α+cos0.5α=根号6/2.一,求cosα的值(已求出为负的根号3/2)二,sin(α-β)=-3/5,β∈(π/2,
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![已知α∈(π/2,π)且sin0.5α+cos0.5α=根号6/2.一,求cosα的值(已求出为负的根号3/2)二,sin(α-...已知α∈(π/2,π)且sin0.5α+cos0.5α=根号6/2.一,求cosα的值(已求出为负的根号3/2)二,sin(α-β)=-3/5,β∈(π/2,](/uploads/image/z/8571310-70-0.jpg?t=%E5%B7%B2%E7%9F%A5%CE%B1%E2%88%88%28%CF%80%2F2%2C%CF%80%29%E4%B8%94sin0.5%CE%B1%2Bcos0.5%CE%B1%3D%E6%A0%B9%E5%8F%B76%2F2.%E4%B8%80%2C%E6%B1%82cos%CE%B1%E7%9A%84%E5%80%BC%EF%BC%88%E5%B7%B2%E6%B1%82%E5%87%BA%E4%B8%BA%E8%B4%9F%E7%9A%84%E6%A0%B9%E5%8F%B73%2F2%EF%BC%89%E4%BA%8C%2Csin%28%CE%B1-...%E5%B7%B2%E7%9F%A5%CE%B1%E2%88%88%28%CF%80%2F2%2C%CF%80%29%E4%B8%94sin0.5%CE%B1%2Bcos0.5%CE%B1%3D%E6%A0%B9%E5%8F%B76%2F2.%E4%B8%80%2C%E6%B1%82cos%CE%B1%E7%9A%84%E5%80%BC%EF%BC%88%E5%B7%B2%E6%B1%82%E5%87%BA%E4%B8%BA%E8%B4%9F%E7%9A%84%E6%A0%B9%E5%8F%B73%2F2%EF%BC%89%E4%BA%8C%2Csin%28%CE%B1-%CE%B2%29%3D-3%2F5%2C%CE%B2%E2%88%88%28%CF%80%2F2%2C)
已知α∈(π/2,π)且sin0.5α+cos0.5α=根号6/2.一,求cosα的值(已求出为负的根号3/2)二,sin(α-...已知α∈(π/2,π)且sin0.5α+cos0.5α=根号6/2.一,求cosα的值(已求出为负的根号3/2)二,sin(α-β)=-3/5,β∈(π/2,
已知α∈(π/2,π)且sin0.5α+cos0.5α=根号6/2.一,求cosα的值(已求出为负的根号3/2)二,sin(α-...
已知α∈(π/2,π)且sin0.5α+cos0.5α=根号6/2.一,求cosα的值(已求出为负的根号3/2)二,sin(α-β)=-3/5,β∈(π/2,π),求cosβ的值?
已知α∈(π/2,π)且sin0.5α+cos0.5α=根号6/2.一,求cosα的值(已求出为负的根号3/2)二,sin(α-...已知α∈(π/2,π)且sin0.5α+cos0.5α=根号6/2.一,求cosα的值(已求出为负的根号3/2)二,sin(α-β)=-3/5,β∈(π/2,
(一)sin(a/2)+cos(a/2)=√6/2.两边平方得:sin²(a/2)+2sin(a/2)cos(a/2)+cos²(a/2)=3/2.===>1+sina=3/2.===>sina=1/2.又sin²a+cos²a=1.===>cos²a=3/4.===>cosa=±√3/2.∵a∈(π/2,π).∴cosa=-√3/2.(二)∵π/2<b<π,π/2<a<π.sin(a-b)=-3/5.∴π/2<a<b<π.且cos(a-b)=4/5.∴cosb=cos[a+(b-a)]=cosacos(b-a)-sinasin(b-a)=cosacos(a-b)+sinasin(a-b)=-(3+4√3)/10.即cosb=-(3+4√3)/10.