If magnitude (absolute value) of vectors ( A + B ) ^2 = A^2 + B^2 then:
a) A and B must be parallel and in the same direction
b) A and B must be parallel and in opposite directions
c) it must be true that either A or B is zero
d) the angle between A and B must be 60 degrees
e) None of the above
I thought the answer was (c) just by foiling out the left side of the equation. but the answer is (e) none of the above, and I'd like an explanation as to why (c) is not correct.