- #1
srfriggen
- 307
- 6
Homework Statement
List the elements of the subgroups <3> and <7> in U(20).
Homework Equations
The Attempt at a Solution
U(20)= {1, 3, 7, 9, 11, 13, 17, 19} = <3> = <7>.
So basically I have that the common elements of, <3> and <7> and U(20), under + modulo 20, are all the elements in U(20). Other than calculating this all out, I reasoned it to be true since 3 and 7 are both coprime to 20.
The answer key in the book has <3>=<7>= {3,9,7,1}.
I believe this is a typo, and that either the answer key is incorrect, or U(20) should be U(10).
Can someone please confirm my suspicion or let me know if I am missing something?