Editing Angle trisection (section)

===Algebraic characterization===
Again, denote the set of [[rational numbers]] by {{math|'''Q'''}}.

[[Theorem]]: An angle of measure {{math|''θ''}} may be trisected [[if and only if]] {{math|''q''(''t'') {{=}} 4''t''<sup>3</sup> − 3''t'' − cos(''θ'')}} is reducible over the [[field extension]]  {{math|'''Q'''(cos(''θ''))}}.

The [[Mathematical proof|proof]] is a relatively straightforward generalization of the proof given above that a {{math|60°}} angle is not trisectible.<ref name=Stewart>{{cite book | last = Stewart | first = Ian  | author-link = Ian Stewart (mathematician) | title = ''Galois Theory'' | publisher = Chapman and Hall Mathematics | year = 1989 | pages = g. 58 | isbn = 978-0-412-34550-0 | title-link = Galois Theory  }}</ref>