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Re: piecewise linear approximation

Subject: Re: piecewise linear approximation
From: "Alex. Lupas"
Date: 30 Apr 2006 00:34:10 -0700
Newsgroups: sci.math
Another remark:

 If f is in C[0,1] , f:[0,1]-->R  is derivable on [0,1], b is fixed in
(0,1),

and the (uni-lateral) derivatives f"(b-) , f"(b+) exist,  then

 following asymptotic formula is valid:

lim_{n-->infty}A_n(b)*( (S_nf)(b) -f(b)-

- B_n(b)*(f"(b+) - f"(b-)) ) =  (f"(b+)+f"(b-))/4  ,


where   S_nf is defined as above (see my posted message)
and

A_n(b)= n^2/( {nb}(1-{nb}) ) ,

B_n(b)= {nb}(1-{nb})(1-2{nb})/(4n^2) .
=========
Likewise, if f is in C[0,1] and the derivatives f'(b+), f'(b-) exist,
then


lim_{n-->infty}C_n(b)*( (S_nf)(b) - f(b) )= ( f'(b+)-f'(b-) )/2

with

C_n(b):=A_n(b)/n= n/({nb}(1-{nb}) ) .


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