已知两角差的余弦公式为cos(x+y)=cosxcosy-sinxsiny,由两角差的余弦公式结合诱导公式,推导两角和的正切公式,推导两角和的正切公式tan(x-y)=(tanx-tany)/(1+tanxtany).
人气：423 ℃ 时间：2020-09-09 01:42:54
解答
cos(x-y)=cosxcosy+sinx+siny
sin(x-y)=cos[90-(x-y)]=sinxcosy-cosxsiny
tan(x-y)=sin(x-y)/cos(x-y)=(tanx-tany)/(1+tanxtany)
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