Below Eq XXXXXXXXXXit is stated that “the linearized solution is an exact solution to the governing equations.” What are the governing equations for which Eq XXXXXXXXXXis a solution? What boundary...

Below Eq. (13.2.59) it is stated that “the linearized solution is an exact solution to the governing equations.” What are the governing equations for which Eq. (13.2.57) is a solution? What boundary conditions are applicable? Where, in fact, was the linearization assumption made in the derivation?