If \(\vec a \:and\: \vec b\) are two vectors such that \(|\vec a + \vec b|= |\vec a - \vec b|=4,\) then which one of the following is correct?

\(\vec a\) must be equal to \(\vec b.\)

\(\vec a \:and\: \vec b\) must be unit vectors.

\(\vec a\) must be parallel to \(\vec b.\)

\(\vec a\) must be perpendicular to \(\vec b.\)

If \(\vec a \:and\: \vec b\) are two vectors such that \(|\vec a + \

1.	If \(\vec a \:and\: \vec b\) are two vectors such that \(\|\vec a + \vec b\|= \|\vec a - \vec b\|=4,\) then which one of the following is correct?
A.	\(\vec a \:and\: \vec b\) must be unit vectors.
B.	\(\vec a\) must be parallel to \(\vec b.\)
C.	\(\vec a\) must be perpendicular to \(\vec b.\)
D.	\(\vec a\) must be equal to \(\vec b.\)
Answer» D. \(\vec a\) must be equal to \(\vec b.\)