English
For a HasCompactMulSupport f with a continuous g, the multiplicative support of the extended function is contained in the image of mulTSupport f under g.
Русский
Мультиподдержка расширенной функции лежит внутри образа mulTSupport f под g.
LaTeX
$$$\\operatorname{mulTSupport}(\\text{extend } g f 1) \\subseteq g''(\\operatorname{mulTSupport}(f)).$$$
Lean4
@[to_additive]
theorem extend_one : HasCompactMulSupport (g.extend f 1) :=
HasCompactMulSupport.of_mulSupport_subset_isCompact (hf.image cont)
(subset_closure.trans <| hf.mulTSupport_extend_one_subset cont)