y=sin(x+y)求导中的（1-cos(x+y))是怎样算出来的

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y=sin(x+y)等式两边同岩镇时对x求导，
y'=cos(x+y)*(1+y');所以y'=cos(x+y)/[1-cos(x+y)]

注意y是顷档x的函数！！！雀枣乱

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解：y'雹改旅=[sin(x+y)]'=cos(x+y)(x+y)'=cos(x+y)(1+y'歼祥)
y'-y'源凳cos(x+y)=cos(x+y)=y'[1-cos(x+y)]=cos(x+y)
y'=cos(x+y)/[1-cos(x+y)]

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