In a statically indeterminate situation, the equations ATy = f do not have a unique solution for the internal forces y in terms of the external forces f.
(a) Prove that, nevertheless, if C = I. the internal forces are the unique solution of minimal Euclidean norm, as given by Theorem 5.59.
(b) Use this method to directly find the internal force for the system in Example 6.1. Make sure that your values agree with those in the example.