1. The problem statement, all variables and given/known data The truss is suspended by two pin joints. Each segment is 3 m wide and 4 m high. The applied force is F = 1 N. What is the force in member 2? 2. Relevant equations Sum of force = 0 3. The attempt at a solution Using method of sections (to get force at 3), so taking the right portion I am trying to understand the sum of the force in the y direction of the section. sum of force y of portion =0 =-1 - J_3 cos(180-arctan(3/4)) My question, do we use 180-angle when looking at the angle, also is it negative J_3, since the J_3 is pointing downwards? I already know that the answer is 1N, I just don't understand this part. Thank you.