已知3sina-2cos=o,求下式的值 (1)(cosa-sina)/(cosa+sina) (2)sin^2a-2s
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已知3sina-2cos=o,求下式的值 (1)(cosa-sina)/(cosa+sina) (2)sin^2a-2sinacosa+4cos^2a
![已知3sina-2cos=o,求下式的值 (1)(cosa-sina)/(cosa+sina) (2)sin^2a-2s](/uploads/image/z/17265842-26-2.jpg?t=%E5%B7%B2%E7%9F%A53sina-2cos%3Do%2C%E6%B1%82%E4%B8%8B%E5%BC%8F%E7%9A%84%E5%80%BC+%EF%BC%881%EF%BC%89%EF%BC%88cosa-sina%29%2F%28cosa%2Bsina%29+%282%29sin%5E2a-2s)
已知3sina-2cos=o
3sina=2cosa
sina/cosa=2/3
(1)(cosa-sina)/(cosa+sina)
=(1-sina/cosa)/(1+sina/cosa)
=(1-2/3)/(1+2/3)
=1/3 / (5/3)
=1/5
(2)sin^2a-2sinacosa+4cos^2a
=(sin^2a-2sinacosa+4cos^2a)/(sin^2a+cos^2a)
=((sina/cosa)^2-2sina/cosa+3)/((sina/cosa)^2+1)
=((2/3)^2-2*2/3+3)/((2/3)^2+1)
=(4/9-4/3+3)/(4/9+1)
=(4-12+27)/(4+9)
=19/13
3sina=2cosa
sina/cosa=2/3
(1)(cosa-sina)/(cosa+sina)
=(1-sina/cosa)/(1+sina/cosa)
=(1-2/3)/(1+2/3)
=1/3 / (5/3)
=1/5
(2)sin^2a-2sinacosa+4cos^2a
=(sin^2a-2sinacosa+4cos^2a)/(sin^2a+cos^2a)
=((sina/cosa)^2-2sina/cosa+3)/((sina/cosa)^2+1)
=((2/3)^2-2*2/3+3)/((2/3)^2+1)
=(4/9-4/3+3)/(4/9+1)
=(4-12+27)/(4+9)
=19/13
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