1. The problem statement, all variables and given/known data Find reaction at A and B. A,B,C are pin joints with a pulley at C. There is a weight hanging from the pulley which is attached just above the joint at D. 2. Relevant equations 3. The attempt at a solution This question can be solved by observation. there are two forces acting on the frame at C. A horizontal and vertical force of the same magnitude which is the tension in the string. BC is a two force member. The FBD is attached. From it I can determine that the reaction at B is tension in the string. member AC has two forces acting on it which are the two different directions of tension in the string. So the weight and the same horizontal force as the force acting on BC. So to conclude the reactions at A and B are of the same magnitude as the weight. But the book draws the horizontal tension in the string twice in the FBD for member AC which results in the horizontal reaction at A being twice as large as what I got. Why does the horizontal force C show up twice?