tan a/2=31-cosa-sina/1+cosa+sina
人气：330 ℃ 时间：2020-05-19 08:18:27
解答
由tan（a/2）=3
得 cosa=[1-tan²（a/2）]/[1+tan²（a/2）]= -4/5
sina=[2tan（a/2）]/[1+tan²（a/2）]= 3/5
所以(1-cosa-sina)/(1+cosa+sina)=3/2
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