## 68 Reputation

17 years, 189 days

## its labled "Numerical...

its labled "Numerical Methods" and its published by PEARSON CUSTOM PUBLISHING ISBN: 0-536-90372-7

## Genious ALEC, PURE...

Genious ALEC, PURE GENIOUS!!! I love you man... god.. makes since why didnt I think of that. use the interpolation as the function. Yep that first one is dead on the money

## Ahhh thats what I was...

Ahhh thats what I was affraid they were asking.... ok so basically: g := x -> (function goes here); h := 0.01; x := 2.5; yayone := (g(x+h)-g(x-h))/(2*h); problem is, they dont give me the function.... just what i put in the post in the quotes... So I am assuming that there is a way to figure out what the function is from only those data points, sadly this was either not covered or I have forgotten how to do this from a previous math course.

## woops that was you that said...

woops that was you that said to use curvefitting... yeah thats pretty much what i tried also. From what you are saying it sounds as though maple can not handle this sort of problem? any chance you could guide me on how to manually do it. your example of (3.2+7)/1=10.2 is not the correct answer according to my book.

## Yes, Thank you for the help...

Yes, Thank you for the help Alec. Also yes I said third, but as you can see from my variable name of yaytwo i meant second derivative, and yeah i got that working, I was still very stumped on how to work the third derivative.... I appreciate the example very much. and yes that also worked like a charm. My final question which somebody suggested to use CurveFitting for I am a little stumped on. I think the main reason is I am not sure what it is the question is asking me to do to begin with. I am going to quote it so that all is clear, then I will explain what I have figured out so far.
" Approximate the derivative of the interpolated function for the following data, using Central Difference method at x=2.5 and using h=0.01 x | Y -------- 2 | -7 3 | 3.2 4 | 4.1 5 |10.45 Hint: You need to interpolate the data because the data point is not in the chart. "
Well I found a couple ways to interpolate the data (This is assuming I am supposed to be interpolating the data to find the correspoding number for an x of 2.5): > g:=unapply(CurveFitting:-Spline([2,3,4,5],[-7,3.2,4.1,10.45],x),x): > g(2.5); -0.8337500066 > with(CurveFitting): > PolynomialInterpolation([[2,-7],[3,3.2],[4,4.1],[5,10.45]], (2.5)); 0.184375000 Firstly, these are different answers... and neither matches the final answer for the problem. So If either of these numbers are correct its only part of what I am supposed to be accomplishing

## I attempted the formula for...

The Example for the third derivative listed in that help file worked like a charm. f := x -> (2*x^2+7)/x; h := 0.01; x := 2; yaytwo := (f(x+h) - 2*f(x) + f(x-h))/h^2;

## denote dy/dx as a function...

Also I need to approximate the derivative of the interpolated function for a table of data, using the Central Difference method at x = 2.5 and h =0.01 x | Y -------- 2 | -7 3 | 3.2 4 | 4.1 5 |10.45 I am not sure what to set my equation for g:= x-> g := x -> x^3+x^2-3*x; h := 0.01; x := 2.5; yaydone := (g(x+h)-g(x-h))/(2*(h));
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