Comments on the Rayleigh-Ritz method
1. Approximating fields must be admissible and should be easy to use such as
polynomial, sine and cosine functions.
2. How many terms should be added in the calculation?
3. What sort of assumption for the field is best?
Above questions are concerned about the convergence of the solution when the number
of terms are increased.
A necessary condition for convergence is that trial field be complete.
A Polynomial series is complete if it is of high enough degree and if no terms are omitted.
Completeness also demands that the lower-order admissible terms be included.