How do I prove that the exponential integral $$f(x)=\int \frac{e^x}{x}\mathrm dx$$ is not an elementary function?
Also, what are the general methods and tricks to prove that an integral or solution to an equation is not an elementary function?
How do I prove that the exponential integral $$f(x)=\int \frac{e^x}{x}\mathrm dx$$ is not an elementary function?
Also, what are the general methods and tricks to prove that an integral or solution to an equation is not an elementary function?