question_answer 1)

If either vector  or . But the converse need not be true. Justify your answer with an example.  

Answer:

Let             either  or cos             Let       and       here       = 3 × 6 + (?6) × 2 + 2 × (?3)       = 18 ? 12 ? 6 = 0.       so we have two non zero vectors  whose produce  is zero.