in truss one...the forces in the member BC and DE have zero. in truss two ... the forces in the members EF and GH have zero.. in truss three ... the forces in the members CD and EF have zero.. Solution in truss one...the forces in the member BC and DE have zero. in truss two ... the forces in the members EF and GH have zero.. in truss three ... the forces in the members CD and EF have zero...