In a mathematical proof (using the induction), when I deal with the base case, which is (if any) correct?
- The case when n=1 is trivial
- The case n=1 is trivial
I would like to know if I need "when" or not.
Since it's unlikely that you're trying to prove n=1, "the case when n=1" is more likely to be appropriate.
Both are correct, but mean slightly different things. "The case n=1" means just that n=1, "the case when n=1" is referring to a broader equation or concept with n, and n is 1. For instance, you are trying to prove that the sum of the sum of the first n odd numbers is n^2 and your base case is n=1.
Source: native speaker of English, studied college-level math