English
For finite index set, the i-th coordinate of b.toDualEquiv f applied to i equals the i-th coordinate of f with respect to the basis, i.e., b.dualBasis.coord i (b.toDualEquiv f) = b.coord i f.
Русский
Пусть ι конечен. Тогда i-я координата b.toDualEquiv(f) по двойственной базе равна i-й координате f по базису: b.dualBasis.coord i (b.toDualEquiv f) = b.coord i f.
LaTeX
$$$ b.dualBasis.coord i (b.toDualEquiv f) = b.coord i f $$$
Lean4
theorem dualBasis_coord_toDualEquiv_apply [Finite ι] (i : ι) (f : M) :
b.dualBasis.coord i (b.toDualEquiv f) = b.coord i f := by simp [-toDualEquiv_apply, Basis.dualBasis]