http://postimage.org/image/8i5i2dtgr/ http://postimage.org/image/8i5i2dtgr/ 1. The problem statement, all variables and given/known data What is the magnitude of the internal force in member BC? 2. Relevant equations So I figured out the reaction force at A and D by taking the moments about point A to find the vertical force at D and then summing the x and y components to find the forces at A. 3. The attempt at a solution So I solved for the reaction forces for A, and D already. Why can't I split the truss into three members? Why can't I take member AD and have a free body diagram for that member and solve for the Fx and Fy for Bx and By by summing the forces? Do I absolutely have to take the moment? Can I not do Ax-Bx=0 Ay-By+Dy=0 To find the components of B? This method doesnt seem to work. Why do I have to take the moment?