h7y23
幼苗
共回答了13个问题采纳率:100% 举报
x=-4,y=3,r=5,sinα=3/5,cosα=-4/5
tanα/【sin(π-α)-cos(π/2+α)】=(-3/4)/[(3/5)+(3/5)]=-3/4X(5/6)=-5/8
tanβ=4/3,3sinβ=4cosβ,9sin^2β=16cos^2β,sin^2β=16/25,sinβ=-4/5,cosβ=-3/5
cos(2α-β)=cos2αcosβ+sin2αsinβ=(1-2sin^2α)cosβ+2sinαcosαsinβ
=[1-2(3/5)^2](-3/5)+2(3/5)(-4/5)(-4/5)=-21/125+96/125=75/125=3/5
1年前
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