English
If f is antiperiodic with c in a NonAssocRing α and β has involutive negation, then f is periodic with period n*(2*c) for any integer n.
Русский
Если f антипериодична с c в NonAssocRing α и β имеет инволютивное отрицание, то f периодична с периодом n*(2*c) для любого целого n.
LaTeX
$$$[NonAssocRing\ α][InvolutiveNeg\ β]\Rightarrow(\forall h:Antiperiodic\ f\ c)(\forall n\in \mathbb{Z})\, Periodic\ f\ (n\cdot (2\cdot c)).$$$
Lean4
theorem int_even_mul_periodic [NonAssocRing α] [InvolutiveNeg β] (h : Antiperiodic f c) (n : ℤ) :
Periodic f (n * (2 * c)) :=
h.periodic_two_mul.int_mul n