English
A map into a product is determined by its projections onto each factor: f = g.prod h if and only if fst ∘ f = g and snd ∘ f = h.
Русский
Отображение в произведение задаётся его проекциями на каждую составляющую: f = g.prod h тогда и только тогда, когда fst ∘ f = g и snd ∘ f = h.
LaTeX
$$$f = g \\mathrm{.prod} h \\iff (\\mathrm{fst} \\circ f) = g \\land (\\mathrm{snd} \\circ f) = h$$$
Lean4
/-- See Note [custom simps projection]. We need to specify this projection explicitly in this case,
because it is a composition of multiple projections. -/
def apply (L₁ : ContinuousMultilinearMap R M₁ M₂) (v : ∀ i, M₁ i) : M₂ :=
L₁ v