From a pedagogical standpoint, this particular translation is not a good lesson to have in the larger lesson-- "conhecido," though still a participle, is being using extremely differently here than in other examples. It's a completely different grammatical structure; this kind of construction should have its own mini-lesson.
Good question! I quote from a battered Living Language course book on Special Consonant Sounds : "ç (used only before a, o, or u) is like c in face:" - I was thinking it mostly seems to be used towards the back end of Portuguese words. Anyway, 'conhecido' can rest easy with the normal 'c' before the 'i' and the first letter has too much of a 'k' sound to it to be any other than a normal c - " c before a, o, and u, and before any other consonant (except h) is like c in cat". Hope this helps!
No, no, it was a great suggestion, the rule that is really complex... not even us natives know exactly when to use... When it comes in the back of the word, like "explicação", it confuses a lot of people, because you can have this "ão" preceeded by "ç" (contenção), by "s" (tensão), or by "ss" (procissão) and they all sound exactly the same!