I mainly am having trouble accurately calculating the force on members in a truss. The reason being is sort of common, my teacher skimmed through the lecture on these calculations, and left the entire class in a fog. I've made my best attempts at researching on the Internet, but so far no real luck. Sure, there a methods on solving the equations, but I would like to know HOW you do it. http://cabot.k12.ar.us/Schools/chs/FacultyWebPages/PowelL/Activity%205_1d--Truss%20calculations.htm The link leads to our exact worksheet containing the problems we need to solve. Now, in regards to the very first truss equation for the top left pin-joint, my teach wrote down: (point A= top left pin-joint / point B=top right pin-joint / point C= bottom left pin-joint) Sigma Force X= 0 -Force AB= 0 Sigma Force Y= 0 -60+ Force AC= 0 Force AC= 60 lbs. I hope you guys understood what I'm trying to say, as it's not easy to write most of this. But what I need to know is, HOW those equations work and where my teach is getting them from. I know how the free body diagrams work, but how do they tie in with the equations? I found out Trigonometry is also used to determine lengths of the members along with angles, but how do they tie in as well? As you can see, to most of you this is a snap, but to me, it is extremely difficult being which I have very few resources at my disposal. I can see that the first problem is explained can be fairly easy, but I do not have any idea how to do the rest of the problems, like #2,3, and 4. Now, I'm not asking you do these problems for me, but please explain to me how I do it. You guys seem like very smart people, and I'd be obliged to any assistance at all.