Two equal vector have a resultant equal to either of them, then the angle between them will be:

Explanation

Hence ` A =F , B =F, R=F, theta= ?`
As ` R^(2) =A^(@) + B^(2) + 2 AV cos theta`
:. ` F^(2) =F^(2) + F^(2) + 2 FF cos theta`
or ` cos theta =- 1/2 =cos 120^(@) or theta = 120^(@)`.