1）∵x=ln(1+t^2) y=t-arctant ∴dx=2tdt/(1+t^2),dy=(1-1/(1+t^2))dt=t^2dt/(1+t^2)故导数dy/dx=[t^2dt/(1+t^2)]/[2tdt/(1+t^2)]=t/2;2）∵y=xlnx ∴dy/dx=1+lnx故d^2y/dx^2=d(dy/dx)/dx=1/x;3）∵y=lnsinx ∴dy=(l...
