1. The problem statement, all variables and given/known data in this question , it's stated in the beginning that there are 6 reactions ... But , the author gave the equation r = n +3 , r = 4 , n = 1 ....It's statically determinate ... 2. Relevant equations 3. The attempt at a solution IMO , the author's is wrong . his original 's intention is to show that the question is statically indetreminate where r > n+3 ( r = 6 , n =1 ) ...so, he broke up beam into 2 parts to solve this question?