Give an example of a relation f such that f = `f^(-1)`

Explanation

Let f = {x,y) in A xx B , x^2 + y^2 = 1}, where A = B = {1, -1 , 0 }
= {(1,0) (0,1),(-1,0),(0,-1)}
`f^(-1)` = {(0,1) (1,0),(0,-1),(-1,0)}
f