已知tanx+1/tanx-1=3,求2sinx-3cosx/4sinx-9cosx;sin^2x-3sinxcosx+1

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已知tanx+1/tanx-1=3,求2sinx-3cosx/4sinx-9cosx;sin^2x-3sinxcosx+1

已知tanx+1/tanx-1=3,求2sinx-3cosx/4sinx-9cosx;sin^2x-3sinxcosx+1
已知tanx+1/tanx-1=3,求2sinx-3cosx/4sinx-9cosx;sin^2x-3sinxcosx+1

已知tanx+1/tanx-1=3,求2sinx-3cosx/4sinx-9cosx;sin^2x-3sinxcosx+1
(tanx+1)/(tanx-1)=3,
tanx=2.
∴(2sinx-3cosx)/(4sinx-9cosx)
=(2tanx-3)/(4tanx-9)
=(2×2-3)/(4×2-9)
=-1.
sin^2x-3sinxcosx+1
=(sin^2x-3sinxcosx)/(sin^2x+cos^2x)+1
=(tan^2x-3tanx)/(tan^2x+1)+1
=(4-3×2)/(4+1)+1
=3/5.