1. The problem statement, all variables and given/known data In this problem , it's a Internal Indeterminate truss . 2. Relevant equations 3. The attempt at a solution So , I remove one of the redundant member , AC and solve the problem . For the first part , I found the real force first . for the second part , I apply the virtual unit force at AC .....I gt my ans = 2.28 , but the ans given is 1.62 . I have checked thru my working many time s, yet I still cant find my mistake , can someone help please??