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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?

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# Homework Help: Need help clarifying statics problem.

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