<P> In mathematics, an identity function, also called an identity relation or identity map or identity transformation, is a function that always returns the same value that was used as its argument . In equations, the function is given by f (x) = x . </P> <P> Formally, if M is a set, the identity function f on M is defined to be that function with domain and codomain M which satisfies </P>

F x x is what type of function