- #1
sara_87
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Homework Statement
this is part of a theorem for the error estimate for the model problem for finite element method.
i have to prove the following inequality:
[tex]\left|u'(x)-\tilde{u}'_h(x)\right|\leq max_{0\leq(y)\leq1}\left|u''(y)\right|[/tex]
Homework Equations
[tex]\tilde{u_h}[/tex] is the interpolant of u, where u is the solution of D (BVP that depends on x).
h is the mesh size.
(it will help a lot if you know about finite element method to understand this question)
The Attempt at a Solution
I don't know how to start but we were told that the mean value theorem is helpful:
u'([tex]\varphi[/tex])=[tex]\frac{u(x_{i+1})-u(x_i)}{x_{i+1}-x_{i}}[/tex]
where x_i to x_(i+1) is one element.
but i don't know how this would help.
I think maybe i don't understand the inequality properly