The question is asking you to prove A ⃗ ⋅(B ⃗ +C ⃗ )=A ⃗ ⋅B ⃗ +A ⃗ ⋅C ⃗ , and the same type of result using × instead of ⋅ . So, of course there have to be three vectors involvedThe question is asking you to prove A ⃗ ⋅(B ⃗ +C ⃗ )=A ⃗ ⋅B ⃗ +A ⃗ ⋅C ⃗ , and the same type of result using × instead of ⋅ . So, of course there have to be three vectors involved