Homework Statement
Let (G, °) be a group such that the mapping f from G into G defined by f(a) = a^(-1) is a homomorphism. Show that (G, °) is abelian.
The Attempt at a Solution
f(a) = a^(-1)
f(a^(-1)) = f(a)^(-1) = (a^-1)^-1 = a
in order for a group to be abelian it needs to...