【急】已知 tanθ=-1/2,求 2sin^2θ-3sinθ*cosθ-6cos^2θ
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【急】已知 tanθ=-1/2,求 2sin^2θ-3sinθ*cosθ-6cos^2θ
【急】已知 tanθ=-1/2,求 2sin^2θ-3sinθ*cosθ-6cos^2θ
【急】已知 tanθ=-1/2,求 2sin^2θ-3sinθ*cosθ-6cos^2θ
2sin^2θ-3sinθ*cosθ-6cos^2θ
=[2(tanθ)^2-3tanθ]/[1+(tanθ)^2]
=[2*1/4+3/2]/(5/4)
=8/5.