SupposeG=〈a〉is a cyclic group of order 12.
Find all of the proper subgroups of G, and list their elements.
Find all the generators of each subgroup. Explain your
reasoning.
Consider the group Z/24Z.
(a) Find the subgroups 〈21〉 and 〈10〉.
(b) Find all generators for the subgroup 〈21〉 ∩ 〈10〉.
(c) In general, what is a generator for 〈a〉 ∩ 〈b〉 in Z/nZ? Prove
your assertion.
Let G be a cyclic group generated by an element a.
a) Prove that if an = e for some n ∈ Z, then G is
finite.
b) Prove that if G is an infinite cyclic group then it contains
no nontrivial finite subgroups. (Hint: use part (a))
Let H and K be subgroups of a group G so that for all h in H and
k in K there is a k' in K with hk = k'h. Proposition 2.3.2 shows
that HK is a group. Show that K is a normal subgroup of HK.
Find all the subgroups of the group of symmetries of a cube.
Show all steps.
Hint: Label the diagonals as 1, 2, 3, and 4 then consider the
rotations to get the subgroups.
Prove that in a finite cyclic group, each subgroup has size dividing the size of the group. Conversely, given a positive divisor of the size of the group, there is a subgroup of that size.