Corollary 8
Tag 01AC, permanent. Cite it as [Bourbaki, Tag 01AC].
Lie Groups and Lie Algebras, chapter IX, § 2. Maximal tori of compact Lie groups
Let H be a compact Lie group, T a maximal torus of H. Then , and the injection of into H induces an isomorphism from to .
Let . Then is a maximal torus of , hence (Th. 2) there exists such that ; thus belongs to , hence the first assertion. The second follows immediately.
Bourbaki sets the proof directly after the statement, and the corpus does not separate them, so what is above is the statement and its proof together.