Question

find generators of U(10)​

Answer 1

U(10) = {1, 3, 7, 9} = {30 , 31 , 33 , 32 } = <3>. Also, {1, 3, 7, 9} = {70 , 73 , 71 , 72 } = <7>. So both 3 and 7 are generators for U(10).  Quite often in mathematics, a “nonexample” is as helpful in understanding a concept as an example.