Use the Flex$\_$M to solve. Select the redundant $($structure is I$-1)$ as the vertical reaction at b$.$ Draw

the shear and moment diagram $($keep a reasonable scale$).$

The doubly fixed beam shown is I$-3$ but due to symmetry the vertical reactions are $\frac{1}{2}$ of the total

load and the horizontal reactions are zero and this allows treating the beam as I$-1.$ Solve and plot

the shear and moment diagram.

Compute the shear and moment diagram for the beam shown.

Since you've solved the beam in P$3$ you know how the reaction at $"$b$"$ relates to the applied moment

Q$.$ Treat the moment Q and the reaction at $"$b$"$ as applied loads and derive the formula for the

rotation at $"$b$".$ Use this formula to compute the ratio of the applied moment Q to the resulting

rotation.