Show that the set {5, 10, 15, 25, 35} is a group under multiplication modulo 40. What is the identity element of this group? - Quora
![SOLVED: Let Un = 1 < k < n | 1 = gcd(k,n). These are the elements of Zn that are relatively prime to n. Note: the book denotes this by U(n). SOLVED: Let Un = 1 < k < n | 1 = gcd(k,n). These are the elements of Zn that are relatively prime to n. Note: the book denotes this by U(n).](https://cdn.numerade.com/ask_images/33372c8a7a4f4d4ab1bd776b330eb6aa.jpg)
SOLVED: Let Un = 1 < k < n | 1 = gcd(k,n). These are the elements of Zn that are relatively prime to n. Note: the book denotes this by U(n).
![SOLVED: Definition 13 The sum of all elements, modulo m Em = C a (mod m) Definition 2 The sum of all invertible elements, modulo m = C (mod m) am Definition SOLVED: Definition 13 The sum of all elements, modulo m Em = C a (mod m) Definition 2 The sum of all invertible elements, modulo m = C (mod m) am Definition](https://cdn.numerade.com/ask_images/8b0b3ed66beb4201bb1260736d23f977.jpg)