Question

求证cosa+1-sina/cosa+1+sina=1-sina/cosa

求证（cosa+1-sina）/(cosa+1+sina)=(1-sina)/cosa

Answer 1

证明；
记 cosa=c sina=s

c/(1-s)=(1+s)/c
[c/(1-s)]+1=[(1+s)/c]+1
(c+1-s)/(1-s)=(c+1+s)/c

倒过来即：
（cosa+1-sina）/(cosa+1+sina)=(1-sina)/cosa

Answer 2

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