|Equlibrium of ..||gives value of forces ...|
|Entire truss||R1 , R2y , R2x|
|Joint A||FAB , FAE|
|Joint B||FBC , FBE|
|Joint E||FCE , FEF|
|Joint F||FCF , FDF|
In principle I am done now. But I have not used one equlibrium equation
on point C and none at point D ( = three unused equations because of
the three global equilibrium equations I used to start with ).
So, I would use these three unused equations to see whether they are satisfied for the values of the forces I previously had obtained. If NOT >>>> I better find my error.
In important note : Only in the rarest of circumstances will you find that
your check-up equations are exactly satisfied. There always will remain
some error due to round-off. So, your problem will be to judge whether
your errors can be explained away by round-off or are due because you
made an honest error somewhere.
My personal strategy of judgement is the following : If I calculate all forces (and angles etc.) to 3 digits accuracy I can at best expect to have my check-up equations satisfied to about 0.1 % (0.01% for 4 digits and so on). My relative error for each equation is calculated the following way : if I get for example 0.5 Newtons (instead of 0 ) and my largest force is 200 newtons my relative error is 0.5/200*100% = 0.25% . It is highly probable that this error is due to round-off. If I would have gotten 2.5 % I would feel very uneasy and check my results.