Question

if a cross b is equals to zero what we can say about the two vectors a and b

Answer 1

they both are Collinear
as,
A x B = ABsin theta
given,
A X B =0
therefore,
ABsin theta = 0
Since the magnitude of A and B can't be 0.
therefore,
sin theta = 0
sin theta = sin 0
hence the angle b/w A and B is zero .
hence they are collinear