If R1 and R2 are two relations or functions, then the result of R3 = R1 × R2 is the combination of tuples that are in R1 and R2. The product is associative and commutative.
Degree (R3) =Degree of (R1) + Degree (R2).
In case, R3 will have tuples such that R3 = {t1 || t2 | R1 ∋ t1 ∧ R2 ∋ t2}.
Example:
R2
A
B
A1
B1
A2
B2
A3
B3
A4
B4
R1
C
C1
C2
R3 = R1 × R2 is