In: Advanced Math
3. (a) Let n ∈ N with n ≥ 2 and consider (Zn, ⊕). If a ∈ Zn, show that a = a −1 if and only if n | 2a. What conditions on n would guarantee that no element is equal to its own inverse?
(b) Let p be prime and consider (Up, ). Under what conditions does a ∈ Up satisfy a = a −1 ? Can you specifically identify the elements that satisfy this condition?