Which of the following is equal to the vector product \(\rm \left(\vec a+\vec b\right)\cdot\left(\vec a-\vec b\right)\)?
1
\(\rm \left|\vec a\right|^2-\left|\vec b\right|^2\)
2
\(\rm \left|\vec a\right|^2+\left|\vec b\right|^2\)
3
\(\rm 2\left|\vec a.\vec b\right|\)
4
0