tana=3,计算(1)(sina+cosa)/(sina-cosa)(2)1/(sin²a-sinacosa
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tana=3,计算(1)(sina+cosa)/(sina-cosa)(2)1/(sin²a-sinacosa-2cos²a)
(sina+cosa)/(sina-cosa)
=(sina/cosa+cosa/cosa)/(sina/cosa-cosa/cosa)
=(sina/cosa+1)/(sina/cosa-1)
=(tana+1)/(tana-1)
=(3+1)/(3-1)
=2
tana=sina/cosa=3
sina=3cosa
(2)1/(sin²a-sinacosa-2cos²a)
=1/(sina-2cosa)(sina+cosa)
=1/(3cosa-2cosa)(3cosa+cosa)
=1/(cosa*4cosa)
=1/4cos²a
=1/[4(1+cos2a)/2]
=1/[2(1+cos2a)]
=1/{2[1+(1-tan²a)/(1+tan²a)]}
=1/{2[1+(1-9)/(1+10)]}
=1/{2[1-8/11]}
=1/{2*3/11}
=1/(6/11)
=11/6
=(sina/cosa+cosa/cosa)/(sina/cosa-cosa/cosa)
=(sina/cosa+1)/(sina/cosa-1)
=(tana+1)/(tana-1)
=(3+1)/(3-1)
=2
tana=sina/cosa=3
sina=3cosa
(2)1/(sin²a-sinacosa-2cos²a)
=1/(sina-2cosa)(sina+cosa)
=1/(3cosa-2cosa)(3cosa+cosa)
=1/(cosa*4cosa)
=1/4cos²a
=1/[4(1+cos2a)/2]
=1/[2(1+cos2a)]
=1/{2[1+(1-tan²a)/(1+tan²a)]}
=1/{2[1+(1-9)/(1+10)]}
=1/{2[1-8/11]}
=1/{2*3/11}
=1/(6/11)
=11/6
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