Approximating polynomials

  • Thread starter EvLer
  • Start date
  • #1
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Homework Statement


find closest function a+bx3 to x2 on the iterval [-1,1]
(we consider standard inner product (f,g) = integral(-1 to 1):fgdx

So, here is my attempt, but I got a suspicious result:

[(1,1) (1,x3)] [a]
[(1,x3) (x3,x3)]
=
[(1,x2)]
[x3, x2)]

then after I've done all the integration I came up with this:
[2 0] [a]
[0 2/7]
=
[1/3]
[0]
which means that x3 term disappears....:frown:
 

Answers and Replies

  • #2
Dick
Science Advisor
Homework Helper
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I can't help you fix it. Because you are completely correct. Why do you think that is suspicious? Find ways to check yourself.
 
  • #3
Dick
Science Advisor
Homework Helper
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619
You are approximating an even function over a symmetric interval. Can adding part of an odd function help you?
 

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