In the previous lesson, the notion of the bi-unit domain was introduced and used to define the basis function. Apart from the knocker delta property other important properties of basis functions are discussed. The meaning of the level basis function is explained. The basis function for global and local nodes is shown. The bi-unit domain makes it very convenient to define the basis function over each element in the subdomain. Combining the local basis functions will lead to the global basis function.
With the discussions in previous lessons, the trial solution and waiting function can be easily written. This is demonstrated for the problem previously defined.