Test Page 2 Title

 For a function , it is known the values for 3 points:
 For a three nodes quadratic element, the interpolation of such function is:


 For this quadratic approach, the resulting expression is:


 and then:

 The following picture shows the error, much bigger outside of the interval.

 If the set of points is:
 that means:
 For the four nodes cubic element, the interpolation of such function is:


 Remember the expression to obtain each :


 therefore:


 The resulting expression is exactly the same to the original one:



