use taylor series result to find value?

Asked by Raphael Hatami

Raphael Hatami (view profile)

on 12 Sep 2019
Latest activity Commented on by John D'Errico

John D'Errico (view profile)

on 12 Sep 2019
Hello, I think this is relatively simple but I can't figure it out. I am computing the taylor series of a function and simply want to evaluate that taylor series result at a specific value x. How can I do this automatically (without copy/pasting the result from the command window)? Thank you
%y = taylor(f,xx,0,1)
syms x
f=@(x) 25*x.^3-6*x.^2+7*x-88;
truevalue = f(3)
T0 = f
T1 = taylor(f,x,1,'Order',1)
T2 = taylor(f,x,1,'Order',2)
T3 = taylor(f,x,1,'Order',3)
result = T3(3)
%T2result = @(x) 70*x - 132
%T2estimate = T2result(3)
%T3result = @(x) 70*x + 69*(x - 1)^2 - 132
%T3estimate = T3result(3)
The result part is what I'm trying to do...

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Answer by David Hill

David Hill (view profile)

on 12 Sep 2019

result=subs(T3,x,3);

John D'Errico

John D'Errico (view profile)

on 12 Sep 2019
Or, you could use matlabFunction to create a function handle that will evaluate the function, converting the symbolic expression into one that will work as a simple function.