须知(e^x)'=e^x,(arctanx)'=1/(1+x²)y=e^arctan(1/x)y'=e^arctan(1/x)·1/[1+(1/x)²]·(-1/x²)=e^arctan(1/x)·x²/(1+x²)·(-1/x²)=e^arctan(1/x)·-1/(1+x²)=-e^arctan(1/x)/(1...