I don't know what "set builder" notation is, but x2 and √x are inverses for x≥0.
The graph of a function and its inverse are symmetric with respect to the line y=x; a graph showing y=x3 and y=x1/3 will show that these two functions are inverses for all real x.
1/x is the inverse of 1/x.
ex and ln x are inverses for x>0
Any straight line perpendicular to y=x will be symmetric to y=x and thus the function representing such a line will be its own inverse, e.g. y=f(x)=1-x.