If \(\vec a\) and \(\vec b\) are unit vector, then correct statement is -
1
\(\rm \vec a+ \vec b\) will never be a unit vector
2
\(\rm \vec a+ \vec b\) is unit vector if \(\vec a\) is parallel to \(\vec b\)
3
\(\rm \vec a+ \vec b\) is unit vector, if \(\vec a\) is perpendicular to \(\vec b\)
4
\(\rm \vec a+ \vec b\) is unit vector, if angle between \(\vec a\) and \(\vec b\) is \(\frac{2\pi}{3}\)