(a) Determine all subfields of . (b) Prove that .
For the first part I think . So, I know about the "Subfield Test", but how would I find the possible subfields to be tested? Or is there a simpler way of dealing with this problem?
For the second part to show they're not isomorphic do I just need to show there is not a one to one correspondance? I think has complex numbers whereas the other one does not...