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Y=Sin(X+Y)这个隐函数的二阶导数,急求!

题目详情
Y=Sin(X+Y)这个隐函数的二阶导数,急求!
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答案和解析
两边对x求导:y'=cos(x+y)(1+y')
得y'=cos(x+y)/[1-cos(x+y)]
所以y"=[-sin(x+y)(1+y')(1-cos(x+y))-cos(x+y)sin(x+y)(1+y')]/[1-cos(x+y)]^2
=-sin(x+y)(1+y')/[1-cos(x+y)]^2
=-sin(x+y)[1+cos(x+y)/(1-cos(x+y))]/[1-cos(x+y)]^2
=-sin(x+y)/[1-cos(x+y)]^3