已知:tana-1/tana=-1,求1/[sina^2+2sina·cosa-(cos^2)·a]得值
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已知:tana-1/tana=-1,求1/[sina^2+2sina·cosa-(cos^2)·a]得值
sina/cosa-cosa/sina=-1
(sin^2a-cos^2a)/sinacosa=-1
sin^2a-cos^2a=-sinacosa
1/[sina^2+2sina·cosa-(cos^2)·a]
=1/sinacosa
=sin^2a+cos^2a/sinacosa
=sina/cosa+cosa/sina
=tana+1/tana
tana-1/tana=-1
tan^2a+1/tan^2a-2=-1
tan^2a+1/tan^2a=1
(tana+1/tana)^2=3
tana+1/tana=+-根号3
(sin^2a-cos^2a)/sinacosa=-1
sin^2a-cos^2a=-sinacosa
1/[sina^2+2sina·cosa-(cos^2)·a]
=1/sinacosa
=sin^2a+cos^2a/sinacosa
=sina/cosa+cosa/sina
=tana+1/tana
tana-1/tana=-1
tan^2a+1/tan^2a-2=-1
tan^2a+1/tan^2a=1
(tana+1/tana)^2=3
tana+1/tana=+-根号3
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