证明； (1) / (tana) + (sina) /(1+cosa) = (1) /(sina)
证明； (1) / (tana) + (sina) /(1+cosa) = (1) /(sina)
其他人气：869 ℃时间：2019-11-11 15:00:58
优质解答
左边=1/(sina/cosa)+sina/(1+cosa)=cosa/sina+sina/(1+cosa)=[cosa(1+cosa)+sin²a]/[sina(1+cosa)]=(cosa+cos²a+sin²a)/[sina(1+cosa)]=(cosa+1)/[sina(1+cosa)]=1/sina=右边命题得证
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