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tAnx=3则sin2x等于多少

tanx=根号3,那么x=60度 sin2x=sin120度=sin60度=根号3/2 cos^2*x =(-1/2)^2=1/4 那么sin2x/1+cos^2*x=2*根号3/5

sin2x-cos2x=2sinxcosx-cosx+sinx=2sinxcosx-cosx+sinx/(cosx+sinx)=2tanx-1+tanx/(1+tanx)=7/5

tanx=-1/3sinx/cosx=-1/3sinx=(-1/3)*cosx(sinx)^2+(cosx)^2=1[(-1/3)*cosx]^2+(cosx)^2=1(cosx)^2=9/10sin2x=2sinx*cosxsin2x=2*(-1/3)*cosx*cosxsin2x=(-2/3)*(cosx)^2sin2x=(-2/3)*(9/10)sin2x=-3/5

sin2x/cos^2x=2sinxcosx/cos^2x=2sinx/cosx=2tanx=2*3=6

作用sin二倍角公式,sin2x=2cosxsinx,代入上式得2cosxsinx/cos^2x,化简得2sinx/cosx=2tanx=6

tan2x=2tanx/(1-tanx^2)=-4/3【sin2x+2cos2x】/【2cosx-3sin2x-1】=【sin2x+2cos2x】/【(2cosx-1)-3sin2x】=【sin2x+2cos2x】/【cos2x-3sin2x】分子分母同时除以cos2x得(tan2x+2)/(1-3tan2x)=2/15

=-24/25

tanx=sinx/cosx=3,而(sinx)^2+(cosx)^2=1,所以sinx=?,cos=?;sin2x=2sinxcosx,将其带入就行了

(1-sin平方x)分之sin2x=sin2x/cos^2x=2sinxcosx/cos^2x=2sinx/cosx=2tanx=6

sin2x=2sinxcosx =2sinxcosx/1 =2sinxcosx/(sinx2+cosx2) =2tanx/(tanx2+1) ∵tanx=2 ∴原式=2*2/(2的平方+1)=4/5

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