If  $|$ $\overrightarrow{A}$ $+$ $\overrightarrow{B}$ $|$ $=$ $\left|\overrightarrow{A}\right|$ $$ $=$ $|$ $\overrightarrow{B}|$ then angle between A and B will be:

1.  $90°$

2. $120°$

3. $0°$

4. $60°$

The vector sum of two forces is perpendicular to their vector difference. In this case, the two forces: 

1. Are equal

2. Have the same magnitude

3. Are not equal in magnitude

4. Cannot be predicted