beam supporting multi-truss sheathed gable end truss in chevron brace

[F1955]

I have a beam supporting a sheathed gable end multi-truss in a chevron brace. What should the unbraced length about the y direction be the entire length or length/2? Thank you

 

[jike]

I always try to brace the bottom flange of the beam where the chevron brace connects to it.