syms t
x=log(sqrt(1+t^2));
y=atan(t);
% 一阶导数
Dyx1 = diff(y,t)/diff(x,t)
% 二阶导数
Dyx2 = diff(Dyx1,t)/diff(x,t)
结果:
Dyx1 = 1/t
Dyx2 = -(t^2 + 1)/t^3