答：d[f(x)]=f'(x)dxd[ln(x+√(x^2+1))]=(1+x/√(x^2+1)/(x+√(x^2+1)) dx即[ln(x+√(x^2+1))]'=(1+x/√(x^2+1)/(x+√(x^2+1)) 由复合函数求导法则易得。
