f(x)= x/1+e^(1/x), x doesn't equal 0
defines a continuous function on R. Is f(x) differentiable?
I have no idea where to even begin. My teacher didn't even teach us this in class before assigning it...
You can get the first part
by taking the limit.
In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.