- #1
oblixps
- 38
- 0
i am having trouble showing that [tex] \mathbb{Q}(\sqrt{p*}) \subset \mathbb{Q}(\zeta_{p}) [/tex] where [tex] p* = (-1)^{\frac{p-1}{2}}p [/tex]. in other words, if p = 1 (mod 4) then p* = p and if p = 3 (mod 4) then p* = -p. i encountered this in the context of galois theory and i have no idea how to start. it seems that i need to know what [tex] \zeta_{p} [/tex] looks like before i decide if [tex] \sqrt{p*} \in \mathbb{Q}(\zeta_{p}) [/tex] but for arbitrary p that is hard to figure out. i also can't figure out why we have the 1 mod 4 and 3 mod 4. can someone give me some hints on this question?