几个导数题x^y=y^xxy=e^(x+y)y=x^(1/y)

来源:学生作业帮助网 编辑:作业帮 时间:2024/11/15 16:35:30

几个导数题x^y=y^xxy=e^(x+y)y=x^(1/y)
几个导数题
x^y=y^x
xy=e^(x+y)
y=x^(1/y)

几个导数题x^y=y^xxy=e^(x+y)y=x^(1/y)
x^y=y^x
两边同时取自然对数,得ylnx=xlny
两边对x求导,得
y'lnx+y/x=lny+xy'/y
∴y'(lnx-x/y)=lny+y/x
∴y'=(lny+y/x)/(lnx-x/y)=(xylny+y^2)/(xylnx-x^2)
xy=e^(x+y)
两边对x求导,得
y+xy'=(1+y')e^(x+y)
∴y'[x-e^(x+y)]=e^(x+y)-y
∴y'=[e^(x+y)-y]/[x-e^(x+y)]
y=x^(1/y)
两边同时取自然对数,得lny=(lnx)/y
即ylny=lnx
两边对x求导,得
y'lny+y(1/y)y'=1/x
即y'(lny+1)=1/x
y'=1/x(lny+1)