5: Cosets, Lagrange’s Theorem, and Normal Subgroups
- Page ID
- 97999
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- 5.2: Lagrange's Theorem
- We’re finally ready to state Lagrange’s Theorem, which is named after the Italian born mathematician Joseph Louis Lagrange. It turns out that Lagrange did not actually prove the theorem that is named after him. The theorem was actually proved by Carl Friedrich Gauss in 1801.