来源：学生作业帮 编辑：作业帮 分类：数学作业 时间：2024/05/16 15:24:32
请问这道二阶求导怎么求
y=tan（x+y）
对y=tan(x+y)求导得
y'=[sec(x+y)]^2*(1+y'),
∴y'*[cos(x+y)]^2=1+y'
-1=y'[sin(x+y)]^2,
y'=-1/[sin(x+y)]^2,
∴y''=2/[sin(x+y)]^3*cos(x+y)*(1+y')
=2/[sin(x+y)]^3*cos(x+y)*{1-1/[sin(x+y)]^2}
=-2[cos(x+y)]^3/[sin(x+y)]^5.
作业帮