Im doing this problem as a part of the experiment for a Basic Roof Truss. I first started off measuring the deflection for each member of the roof truss (member dismantled from the roof structure) by applying certain amounts of weights. Next I put all the members up into a roof structure as shown in the picture with 60 degrees at each vertex. Im required to find the forces in each of the member thereotically to compare with my experimental results. Im having problems finding the forces in each member thereotically. The attempt at a solution In the second diagram,I started by using the parallelogram method and sine rule to find the magnitude of force in member A and B. As a result, Fa and Fb has the same magnitude. Then by using Fa , I used sine rule to obtain Fc as shown in the second diagram. The magnitude of forces i obtain each are about 50% error. The results i obtain in my experiment shows significant different amount of forces in each member. Could someone please show me the way to calculate the forces in the members? Thank you in advance.