sadguljawelrkgrs
幼苗
共回答了14个问题采纳率:100% 举报
cotxcosx/(cotx-cosx)=cosx/(1-sinx)=(cos^2x/2-sin^2x/2)/(sin^2x/2+cos^2x/2+2sinx/2cosx/2)=(cos^2x/2+sin^2x/2)(cos^2x/2-sin^2x/2)/(sin^2x/2-cos^2x/2)^2=(cosx/2+sinx/2)/(cosx/2-sinx/2)=(tanx/2+1)/(1-tanx/2)=tan(x/2+派/4),得证
1年前
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