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Section6.6Exercises

Throughout, write all permutations using disjoint cycle notation, and write all dihedral group elements in standard form.

1

Let σ=(134), τ=(23)(145), ρ=(56)(78), and α=(12)(145) in S8. Compute the following.

  1. στ

  2. τσ

  3. τ2

  4. τ1

  5. o(τ)

  6. o(ρ)

  7. o(α)

  8. τ

2

Prove Lemma 6.3.4.

3

Prove that An is a subgroup of Sn.

4

Prove or disprove: The set of all odd permutations in Sn is a subgroup of Sn.

5

Let n be an integer greater than 2. m{1,2,,n}, and let H={σSn:σ(m)=m} (in other words, H is the set of all permutations in Sn that fix m).

  1. Prove that HSn.

  2. Identify a familiar group to which H is isomorphic. (You do not need to show any work.)

6

Write rfr2frfr in D5 in standard form.

7

Prove or disprove: D6S6.

8

Which elements of D4 (if any)

  1. have order 2?

  2. have order 3?

9

Let n be an even integer that's greater than or equal to 4. Prove that rn/2Z(Dn): that is, prove that rn/2 commutes with every element of Dn. (Do NOT simply refer to the last statement in Theorem 6.5.10; that is the statement you are proving here.)