You have a linear system with four equations and four variables.
The solution can be seen with the naked eye to be D1=D2=D3=D4=0.
Don't expect Prime's symbolics to come up with something different.
The system either has one unique solution (all zeros) or an infinite number of solutions, in case the coefficient matrix is zero (e.g. if L = 0 or if a=0).
Thank you for the reply. I am new to structural dynamics, and I am sorry if this problem was obvious. Actually, I wanted to solve the mode shape for continuous beams at different locations if I knew the end conditions. I have set up the equation of mode shape in this new matched file. The author didn't solve the equation in his textbook, and it was difficult for me to solve by hand calculation. I don't know if Mathcad can provide the solution to this.
I don't know anything about structural dynamics, but a linear system where on the right hand side of each equation the term not dependent on the variables is zero either has the trivial solution of all variable being zero or has an infinite number of solutions if the equations are linear dependent.
Unfortunately, I can't help you set up the equations for your problem, but I can help you solving them and with the usage of Prime.
