Problem 2
Part a
Prove that for U(13), the function formula P5(x) = x^5 is an automorphism of U(13).
Part b
Determine the integers n less than or equal to 12 such that Yn(x) is an automorphism of U(13). You do not need to give a complete proof of your answer, but you should give at least enough work to determine a pattern.
Part c
Based on your work in Part a and Part b, state a general claim about when, for an integer n and a prime p, the function Yn(x) = x^n is an automorphism of U(p).