若tana=2则sin^2a+sinacosa

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如唯禅知图设袭宏ab=x,因为tana=2,所以bc=2x,则ac=√5x,

所指消以sin^2a+sinacosa=4/5+2/5=6/5

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sin^2a+sinacosa=cos^2a(tan^2a+tana)=6cos^2a=6/csc^2a=6/(1+tan^-2a)=24/5

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