acc to the formal definition of 3NF:
This definition states that a table is in 3NF if and only if, for each of its functional dependencies X → A, at least one of the following conditions holds:
- X contains A (that is, X → A is trivial functional dependency), or
- X is a superkey, or
- Every element of A-X, the set difference between A and X, is a prime attribute (i.e., each attribute in A-X is contained in some candidate key)
so since Primary key is also a Superkey therefore it satisfies the second condition, and hence relation is in 3NF.
