Which one of the following is not true?
1
\(|\overrightarrow a | = |\overrightarrow b | \Rightarrow \overrightarrow a = \overrightarrow b \)
2
\({\left| {\vec a \times \vec b} \right|^2} = {\left( {\vec a} \right)^2}{\left( {\vec b} \right)^2} - {\left( {\vec a.\vec b} \right)^2}\;\)
3
\(\vec a \times \left( {\vec b\;.\;\vec c\;} \right)\)
4
If the adjacent sides of a parallelogram are represented by the vectors \(\vec a\) and \(\vec b\) respectively, then its area is \(|\vec a \times \vec b|\)