①$$f(x)=\sin x$$，$$g(x)=\sqrt{1-\cos x}$$

②$$f(x)=\ln(\sqrt{x^2+1}-x)$$，$$g(x)=-\ln(\sqrt{x^2+1}+x)$$

③$$f(x)=\sqrt[3]{x^4-x^3}$$，$$g(x)=x\sqrt[3]{x-1}$$

④$$f(x)=\ln(x^2-1)$$，$$g(x)=\ln(x-1)+\ln(x+1)$$

⑤$$f(x)=\ln x^3$$，$$g(x)=3\ln x$$

⑥$$f(x)=e^{\frac{1}{2}\ln x}$$，$$g(x)=\frac{1}{\sqrt{x}}$$

⑦$$f(x)=\tan x$$，$$g(x)=\frac{1}{\cot x}$$