Question

for what angle between vector p and vector q the value of qvector is multiply vector p is maximum

Answer 1

Since Square of resultant is equal to A^2 +B^2 + 2ABcos[angle between them] therefore the angle should be 0 or 2π. Hope you like the answer.                                                                                                   A and B are two vectors as per your questions they are respective as p and q vectors.