1.sin7°+cos15°sin8°/cos7°-sin15°cos8°=2.已知π/2<β<3π/4,cos(α-β)=12/13,sin(α+β)=-3/5,求sin2α的值.3.已知sin(2α+β)+2sinβ=0,求证tanα=3tan(α+β)4.已知向量a=(cosα,sinα) b=(cosβ,sinβ),|向量a-向量
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![1.sin7°+cos15°sin8°/cos7°-sin15°cos8°=2.已知π/2<β<3π/4,cos(α-β)=12/13,sin(α+β)=-3/5,求sin2α的值.3.已知sin(2α+β)+2sinβ=0,求证tanα=3tan(α+β)4.已知向量a=(cosα,sinα) b=(cosβ,sinβ),|向量a-向量](/uploads/image/z/2482754-50-4.jpg?t=1.sin7%C2%B0%2Bcos15%C2%B0sin8%C2%B0%2Fcos7%C2%B0-sin15%C2%B0cos8%C2%B0%3D2.%E5%B7%B2%E7%9F%A5%CF%80%2F2%EF%BC%9C%CE%B2%EF%BC%9C3%CF%80%2F4%2Ccos%EF%BC%88%CE%B1-%CE%B2%EF%BC%89%3D12%2F13%2Csin%EF%BC%88%CE%B1%2B%CE%B2%EF%BC%89%3D-3%2F5%2C%E6%B1%82sin2%CE%B1%E7%9A%84%E5%80%BC.3.%E5%B7%B2%E7%9F%A5sin%EF%BC%882%CE%B1%2B%CE%B2%EF%BC%89%2B2sin%CE%B2%3D0%2C%E6%B1%82%E8%AF%81tan%CE%B1%3D3tan%EF%BC%88%CE%B1%2B%CE%B2%EF%BC%894.%E5%B7%B2%E7%9F%A5%E5%90%91%E9%87%8Fa%3D%EF%BC%88cos%CE%B1%2Csin%CE%B1%29+b%3D%28cos%CE%B2%2Csin%CE%B2%29%2C%7C%E5%90%91%E9%87%8Fa-%E5%90%91%E9%87%8F)
1.sin7°+cos15°sin8°/cos7°-sin15°cos8°=2.已知π/2<β<3π/4,cos(α-β)=12/13,sin(α+β)=-3/5,求sin2α的值.3.已知sin(2α+β)+2sinβ=0,求证tanα=3tan(α+β)4.已知向量a=(cosα,sinα) b=(cosβ,sinβ),|向量a-向量
1.sin7°+cos15°sin8°/cos7°-sin15°cos8°=
2.已知π/2<β<3π/4,cos(α-β)=12/13,sin(α+β)=-3/5,求sin2α的值.
3.已知sin(2α+β)+2sinβ=0,求证tanα=3tan(α+β)
4.已知向量a=(cosα,sinα) b=(cosβ,sinβ),|向量a-向量b|=2√2/5
(1)求cos(α-β)的值.
(2)若0<α<π/2,-π/2<β<0,且sinβ=-5/13,求sinα
1.sin7°+cos15°sin8°/cos7°-sin15°cos8°=2.已知π/2<β<3π/4,cos(α-β)=12/13,sin(α+β)=-3/5,求sin2α的值.3.已知sin(2α+β)+2sinβ=0,求证tanα=3tan(α+β)4.已知向量a=(cosα,sinα) b=(cosβ,sinβ),|向量a-向量
1.[sin7°+cos15°sin8°]/[cos7°-sin15°sin8°]
=[sin(15°-8°)+cos15°sin8°]/[cos(15°-8°)-sin15°sin8°]
=【sin15°cos8°-cos15°sin8°+cos15°sin8°]/[cos15°cos8°+sin15°sin8°-sin15sin8°]=tan15°=tan(45°-30°)=(3-根号3)/(3-根号3)=(3/2 ) -根号3.
2.因为 π/2<β<3π/4,sin(α+β)=-3/5