tanx=2 求sin^2x+sinxcosx-3cos^2x

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tanx=2 求sin^2x+sinxcosx-3cos^2x
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tanx=2 求sin^2x+sinxcosx-3cos^2x
tanx=2 求sin^2x+sinxcosx-3cos^2x

tanx=2 求sin^2x+sinxcosx-3cos^2x
tanx=2
sinx/cosx=2
sinx=2cosx
(sinx)^2+(cosx)^2=5(cosx)^2=1
(cosx)^2=1/5
(sinx)^2+sinxcosx-3(cosx)^2
=(cosx)^2(4+2-3)
=3(cosx)^2
=3/5