Question

y=ln(x²+1) 求dy

Answer 1

复合求导

[f(g(x))]=f'(g(x))*g'(x)

所以这里f(x)=ln x,g(x)=x^2+1

所以f'(x)=1/x

f'(g(x))=1/(x^2+1)

g'(x)=2x

所以dy=(1/(x^2+1)*2x)dx=2xdx/(x^2+1)