作业帮若cos(π/4-θ)cos(π/4+θ)=√2/6,且0
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若cos(π/4-θ)cos(π/4+θ)=√2/6,且0
若cos(π/4-θ)cos(π/4+θ)=√2/6,且0<θ<π/2,则sin2θ
若cos(π/4-θ)cos(π/4+θ)=√2/6,且0
为了方便p用来表示派 a用来表示角 @表示根号
Cos(p/4-a)cos(p/4+a)=cos(a-p/4)cos(a+p/4)=@2/6
Cos(p/4-a)cos(a+p/4)-sin(p/4-a)sin(p/4+a)=cos(p/4-a+a+p/4)=cosp/2=0
所以 sin(p/4-a)sin(p/4+a)=@2/6
所以sin(a-p/4)sin(p/4+a)=-@2/6
Cos2a=cos(a-p/4+a+p/4)=cos(a-p/4)cos(a+p/4)-sin(a-p/4)sin(a+p/4)=@2/3
所以sin2a=@7/3
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若cos(π/4-θ)cos(π/4+θ)=√2/6,且0
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