Proposition 5
Tag 0DN7, permanent. Cite it as [Bourbaki, Tag 0DN7].
Algebra, chapter IX, § 8. Types de formes quadratiques
*We suppose that A is a maximal ordered field. Let Q be a non-degenerate quadratic form of finite dimension over A, and its signature (, no 2, def. 2). Then the type of Q is , and the group of types of quadratic forms over A is an infinite monogenic group generated by .
Indeed, since is of order 2 and , is generated by and is therefore monogenic. For every , is the type of the positive non-degenerate quadratic forms of dimension ; since these forms are not neutral, we have , which shows that is infinite. Finally, a form of signature is isomorphic, with the notation of prop. 4, to the direct sum of forms and of forms (§ 7, n° 2, th. 1); it follows that its type is .
Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.
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