From the geometry of deformation equation...
... solve for the reaction force RA:
We've solved for the reaction force RA by considering the superposition of two cantilever beam cases. Having determined one of the unknown reactions, the remaining two unknowns (i.e., the reaction force at B and the reaction moment at B) can be solved with statics.
Next, we solve the same problem by
considering the superposition of two
simply supported beam cases.