Algebra Homework 5

Algebra Homework 5
Due by the start of class on Wednesday Nov. 5
Problem 1:
1. Draw steps for how to bisect an angle using a straightedge and compass. You
shouldn’t need more than two or three pictures, and you don’t have to “prove”
that your method actually bisects the angle. A convincing picture is enough.
2. Prove that if a regular n-gon is constructible, then a regular 2n-gon is also constructible. Your “proof” should consist of a precise description of how to construct
the 2n-gon.
Problem 2: Prove that π 2 − 1 is algebraic over Q(π 3 ).
√ √ √ √
Problem 3: Prove that Q( 3, 3 3, 4 3, 5 3, . . . ) is an algebraic field extension of Q, but that
it is not finite.
Problem 4: Let F be a field and E be the splitting field for a polynomial f (x) ∈ F [x], where
deg(f (x)) = n.
1. Show that [E : F ] ≤ n!. (the exclamation point denotes factorial).
2. Let p be any prime number bigger than n. Show that p does not divide [E : F ].
Problem 5: Describe the splitting field for x4 − x2 − 2 ∈ Z3 [x].