若sina+cosa/sina-cosa=2则4sin^2a-3sinacosa-5cos^2a=?tana=-1(-pai小于a小于pai)则a=

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若sina+cosa/sina-cosa=2则4sin^2a-3sinacosa-5cos^2a=?tana=-1(-pai小于a小于pai)则a=

若sina+cosa/sina-cosa=2则4sin^2a-3sinacosa-5cos^2a=?tana=-1(-pai小于a小于pai)则a=
若sina+cosa/sina-cosa=2则4sin^2a-3sinacosa-5cos^2a=?tana=-1(-pai小于a小于pai)则a=

若sina+cosa/sina-cosa=2则4sin^2a-3sinacosa-5cos^2a=?tana=-1(-pai小于a小于pai)则a=
若sina+cosa/sina-cosa=2
sina+cosa=2sina-2cosa
sina=3cosa
tana=3
则4sin^2a-3sinacosa-5cos^2a=(4sin^2a-3sinacosa-5cos^2a)/(sin^2a+cos^2a),(分子分母同除以cos^2a)
=(4tan^2a-3tana-5)/(tan^2+1)
=(4*9-3*3-5)/(9+1)
=22/10
=11/5
tana=-1(-pai小于a小于pai)则a=-Pai/4