Find the derivative of f(a)=ln(a2+1)f(a) = \ln(a^2 + 1)f(a)=ln(a2+1).
1a2+1\frac{1}{a^2+1}a2+11
2aa2+1\frac{2a}{a^2+1}a2+12a
aa2+1\frac{a}{a^2+1}a2+1a
2aln(a2+1)2a \ln(a^2+1)2aln(a2+1)