y=√[1+(lnx)^2]
y'=2lnx*(1/x)*(1/2√1+(lnx)^2)
=(1/x)lnx*(1/√1+lnx^2)
y'|x=e =(1/e)*(1/√2)=1/(e√2)最后答案是√2/2e呢1/(e√2)=(1/√2)(1/e)=(√2/2e)