(sina-cosa)/(3sina+cosa)=1/7那么tana=?

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(sina-cosa)/(3sina+cosa)=1/7那么tana=?
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(sina-cosa)/(3sina+cosa)=1/7那么tana=?
(sina-cosa)/(3sina+cosa)=1/7那么tana=?

(sina-cosa)/(3sina+cosa)=1/7那么tana=?
左边上下除以cosa得到方程(tana简写为t):(t-1)/(3t+1)=1/7,解得t=2

(sina-cosa)/(3sina+cosa)=1/7
(sina/cosa-1)/(3sina/cosa+1)=1/7
(tana-1)/(3tana+1)=1/7
tana=2

(sina-cosa)/(3sina+cosa) (同时除以cosa)
=(tana-1)/(3tana+1)
=1/7
∴7tana-7=3tana+1
4tana=8
∴tana=2