Verify (a + b) × (a + b) = 0
What numbers can go into the equation as vector A(coordinates) and what numbers can go into the equation as vector B (coordinates) in order for the answer to be 0???
the point is, that any numbers will produce zero. You just have to remember that the cross product distributes:
(a+b)x(a+b) = axa + bxa + axb + bxb
since axa = bxb = 0
and
axb = -bxa
the sum is zero.