1.tanα=1/3 tan(β-α)=-2 求tanβ2.若cosα=-1/2 sinβ=-√3/2求α∈(π/2,π)β∈(3π/2,2π)求sin(α+β)

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1.tanα=1/3 tan(β-α)=-2 求tanβ2.若cosα=-1/2 sinβ=-√3/2求α∈(π/2,π)β∈(3π/2,2π)求sin(α+β)
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1.tanα=1/3 tan(β-α)=-2 求tanβ2.若cosα=-1/2 sinβ=-√3/2求α∈(π/2,π)β∈(3π/2,2π)求sin(α+β)
1.tanα=1/3 tan(β-α)=-2 求tanβ
2.若cosα=-1/2 sinβ=-√3/2求α∈(π/2,π)β∈(3π/2,2π)求sin(α+β)

1.tanα=1/3 tan(β-α)=-2 求tanβ2.若cosα=-1/2 sinβ=-√3/2求α∈(π/2,π)β∈(3π/2,2π)求sin(α+β)
一.(tanβ - tanα)/(1 - tanβ * tanα) = -2
∵tanα = 1/3
∴ (tanβ - 1/3)/(1 - tanβ * 1/3) = -2
tanβ - 1/3 = -2(1 - 1/3 * tanβ)
3tanβ - 1 = -6 + 2tanβ)
解得tanβ=5
二.
∵α∈(π/2,π) cosα =- 1/2 (π/2,π 象限为第二象限所以sinα为正数)
∴ sinα=√(1 - 1/4)= √3/2 (3π/2,2π 象限为第四象限所以cosβ为正数)
∵β∈(3π/2,2π) sinβ =- √3/2
∴cosβ=√(1-3/4)=1/2
sin(α+β)=sinαcosβ + cosαsinβ
=√3/2 * 1/2 +(-1/2) * (=-√3/2)
=√3/2

1.tanβ=-5
2.sin(α+β) =√3/2