Das ist durchaus so -> vs -> .. unbedingt so.
From what I understand both durchaus AND unbedingt mean "definitely, absolutely" and such.
So I was wondering if they really mean the same thing the same way.
1) Are these sentences correct German?
Das ist durchaus so. Das ist unbedingt so.
2) Are they the same?
3) If not, what would be the difference(s)?
These sentencs are not the same. If one is wondering about something, like "books become cheaper over time", you can say "Das ist durchaus so." and confirm this thought. "Das ist unbedingt so." means that it must be that way. "unbedingt" means in such a context "without a condition" (condition = Bedingung). So "Das ist unbedingt so." means that whatever is true without any conditions to be fulfilled.
A synonym for "durchaus" could be "wirklich". A not quite synonym for "unbedingt" would be "zwangsläufig".