化简cosθ+cos(θ+2π/3)+cos(θ+

化简cosθ+cos(θ+2π/3)+cos(θ+4π/3)

1个回答

原式=cosθ+cosθcos2π/3-sinθsin2π/3+cosθcos4π/3-sinθsin4π/3
=cosθ+cosθ*(-1/2)-sinθ*√3/2+cosθ*(-1/2)-sinθ*(-√3/2)
=0

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