企源知识库

设y=arctane^x+arctane^-x，则dy=_____．
【正确答案】：y'=[e^x/(1+e^2x)]-[e^-x/(1+e^-2x)]=[e^x/(1+e^2x)]-[e^-xe^2x/(1+e^-2x)e^2x]=[e^x/(1+e^2x)]-[e^x/(1+e^2x)]=0，dy=0．