For the system and freebody diagram as shown in Figure 1 wri

For the system and free-body diagram as shown in (Figure 1), write the equilibrium equation along the y direction

Force FC is in XZ Plane.

Force FB is along Y direction.

Force FB vector= FB j

Where j = unit vector along Y axis

Force FD is in XY plane.

ForceFD vector = FD sin 30(-i) + FD cos 30 (-j)

Where i = unit vector along X axis.

So,Equilibrium equation along Y axis is , Net force force along Y axis = 0

FB j+(FD cos 30 )(-j) = 0 Since there is only two forces along Y axis

FB -FD cos 30 = 0