1.
dy={arctanx+x/(1+x^2) -1/2*[2x/(1+x^2)]}dx
2.
y'=(6x)sec^2(3x^2+1)
3.
f'(x)=2cos(a^x+1/x)*[-sin(a^x+1/x)]*(a^xlna-1/x^2)