In: Advanced Math
Abstract Algebra
Let n ≥ 2. Show that Sn is generated by each of the following sets.
(a) S1 = {(1, 2), (1, 2, 3), (1, 2, 3, 4), ..., (1, 2, 3,..., n)}
(b) S2 = {(1, 2, 3, ..., n-1), (1, 2, 3, ..., n)}
We know that 
 is generated by the
subset of all transpositions in it.
a) Now, observe that 
Thus, if 
 is the subgroup of
generated by 
 then we have

But then, 
 for every integers 
. That is, 
 contains all the transpositions in 
 . Hence, 
.
b) Now, observe that 
. Thus, if 
 is the subgroup of
generated by 
 then we have

But then, for every integers 
, we have

for every integers 
; this is because 
 is a transposition as conjugation preserves cycle structure, and
 sends 
 to 
 . Thus, 
 contains all the transpositions in 
 . Hence, 
.