若tanθ=根号3/3,则cos^2θ-sin(θ+π/6)cosθ的值

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若tanθ=根号3/3,则cos^2θ-sin(θ+π/6)cosθ的值

若tanθ=根号3/3,则cos^2θ-sin(θ+π/6)cosθ的值
若tanθ=根号3/3,则cos^2θ-sin(θ+π/6)cosθ的值

若tanθ=根号3/3,则cos^2θ-sin(θ+π/6)cosθ的值
tanθ=√3/3,θ=kπ+π/6,
k为偶数时
cos^2θ-sin(θ+π/6)cosθ
=3/4-√3/2*√3/2=0
k为奇数时
cos^2θ-sin(θ+π/6)cosθ
=3/4-3/4=0

cos^2θ-sin(θ+π/6)cosθ=-cos(π/6)sinθcosθ+(1/2)*cos^2(θ)
=cos^2(θ)*(-cos(π/6)tanθ+1/2)
=[1/(tan^2(θ)+1)])*(-cos(π/6)tanθ+1/2)
=0