How Accurate Is the Analytical Method for Calculating Truss Forces?

[Stacyg]

Hi. The question is attached as well as my attempt at the answer, which I'm pretty sure is at least partially wrong. I have'ne included my calculations at point B as I have uploaded the limit of 3 files but I got BC=18.30kN (compression)
Any help would be great thanks.

 

[nvn]

I'm having some trouble with legibility of the files; so I only checked joint A. Although I cannot really read it, it appears everything at joint A is correct, except on your free-body diagram you assumed the force in member AD is compression. Then when that force variable turned out to be negative, you claimed the force is compression. That is incorrect. Negative means the force is the opposite of the direction you assumed for the unknown vector in your free-body diagram. Try it again.