[tikhonj]

People don't generally use "proofed" like that—I would always use "proven" to talk about something that had a mathematical proof, and "proofed" only comes up in specialized areas like publishing (where it's used as the past tense of making a proof of something to be printed or as short for "proofread").

[gricardo99]

proofed is also used at times in a baking context, such as proofing dough (i.e. sufficiently risen due to maturity of the yeast culture)

Otherwise I agree, as a native english speaker I’m not familiar with it being used in engineering/mathematics contexts.

[bloak]

I use "proved" for mathematics. For me (middle-aged British) "proven" sounds a bit pompous and rhetorical, not the sort of language an honest down-to-earth mathematician would use.