tana=3,则(2sin^3a+cosa)/(cos^3a-sin^2a×cosa)=

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tana=3,则(2sin^3a+cosa)/(cos^3a-sin^2a×cosa)=
tana=3,则(2sin^3a+cosa)/(cos^3a-sin^2a×cosa)=

tana=3,则(2sin^3a+cosa)/(cos^3a-sin^2a×cosa)=
原式=[2tanα(sinα)^2+1]/[(cosα)^2-(sinα)^2]
  =[6(sinα)^2+(cosα)^2+(sinα)^2]/[cosα)^2-(sinα)^2]
  =[7(tanα)^2+1]/[1-(tanα)^2]
  =(7×3^2+1)/(1-3^2)
  =(63+1)/(1-9)
  =-8