English
If B is nondegenerate and symmetric, then for any basis b, B.dualSubmodule (B.dualSubmodule (span_R(range b))) = span_R(range b).
Русский
Если B ненадежна и симметрична, то для любого базиса b выполняется B.dualSubmodule(B.dualSubmodule(span_R(range b))) = span_R(range b).
LaTeX
$$$$ \text{If } B \text{ is nondegenerate and symmetric, then } B.dualSubmodule( B.dualSubmodule(\mathrm{span}_R(\mathrm{range}\, b)) ) = \mathrm{span}_R(\mathrm{range}\, b). $$$$
Lean4
/-- Apply a linear map to the left argument of a bilinear form. -/
def compLeft (B : BilinForm R M) (f : M →ₗ[R] M) : BilinForm R M :=
B.comp f LinearMap.id