几道数学题,求 急用!1.已知cosΘ=-3/5,Θ∈(π/2,π),求sin(Θ+π/3)的值.2.已知sinΘ=-12/13,Θ是第三象限角,求cos(π/6+Θ)的值.3.已知tan α=3,求tan(α+π/4)的值.
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![几道数学题,求 急用!1.已知cosΘ=-3/5,Θ∈(π/2,π),求sin(Θ+π/3)的值.2.已知sinΘ=-12/13,Θ是第三象限角,求cos(π/6+Θ)的值.3.已知tan α=3,求tan(α+π/4)的值.](/uploads/image/z/1142990-62-0.jpg?t=%E5%87%A0%E9%81%93%E6%95%B0%E5%AD%A6%E9%A2%98%2C%E6%B1%82+%E6%80%A5%E7%94%A8%211.%E5%B7%B2%E7%9F%A5cos%CE%98%3D-3%2F5%2C%CE%98%E2%88%88%EF%BC%88%CF%80%2F2%2C%CF%80%EF%BC%89%2C%E6%B1%82sin%28%CE%98%2B%CF%80%2F3%EF%BC%89%E7%9A%84%E5%80%BC.2.%E5%B7%B2%E7%9F%A5sin%CE%98%3D-12%2F13%2C%CE%98%E6%98%AF%E7%AC%AC%E4%B8%89%E8%B1%A1%E9%99%90%E8%A7%92%2C%E6%B1%82cos%EF%BC%88%CF%80%2F6%2B%CE%98%29%E7%9A%84%E5%80%BC.3.%E5%B7%B2%E7%9F%A5tan+%CE%B1%3D3%2C%E6%B1%82tan%28%CE%B1%2B%CF%80%2F4%EF%BC%89%E7%9A%84%E5%80%BC.)
几道数学题,求 急用!1.已知cosΘ=-3/5,Θ∈(π/2,π),求sin(Θ+π/3)的值.2.已知sinΘ=-12/13,Θ是第三象限角,求cos(π/6+Θ)的值.3.已知tan α=3,求tan(α+π/4)的值.
几道数学题,求 急用!
1.已知cosΘ=-3/5,Θ∈(π/2,π),求sin(Θ+π/3)的值.
2.已知sinΘ=-12/13,Θ是第三象限角,求cos(π/6+Θ)的值.
3.已知tan α=3,求tan(α+π/4)的值.
几道数学题,求 急用!1.已知cosΘ=-3/5,Θ∈(π/2,π),求sin(Θ+π/3)的值.2.已知sinΘ=-12/13,Θ是第三象限角,求cos(π/6+Θ)的值.3.已知tan α=3,求tan(α+π/4)的值.
1.sin(Θ+π/3)=sinΘcosπ/3+cosΘsinπ/3
=1/2sinΘ+(-3/5)*√3/2
而sinΘ=√(1-cos2Θ)=0.8(由于其在第二象,因此值为正,其中的2为平方)
因此:原式=1/2*4/5-3√3/10
=(4-3√3)/10
2 cos(π/6+Θ )=cos π/6cos Θ-sin π/6sin Θ
= √3/2 cos Θ –1/2*(-12/13)
而cosΘ=√(1-sin2Θ)=-5/13 余弦在第三象限为负值,其中.
因此,原式=√3/2×(-5/13)-1/2×(-12/13)
=(12-5√3)/26
3.tan(+π/4)=(tan α +tan π/4)/(1-tan π/4×tan α)
=(3+1)/(1-3×1)
=-2
1 因为cosΘ=-3/5所以sinΘ=1-(cosΘ)2(平方)(要开方)=4/5
所以sin(Θ+π/3)=sinΘcosπ/3+cosΘsinπ/3=0