Why does matlab not evaluate equations properly?

I'm trying to evaulate taylor series at x = 6.42855, however with my equation it does not evaluate it at that point and just outputs the taylor series. What should i do to fix it? Anyone able to write a better code for this?

[Balaji Udayagiri]

Hi Lin Wu,

As per my understanding, you want to evaluate the Taylor expansion at a particular point.

Here is how you can modify your code:

clearvars
clc
syms x
f = log(0.7*x+0.5);
x0 = 4.2857;
t0 = taylor(f,x,x0,'Order',2);
h = subs(t0,x,6.42855);

You can refer to the following link for documentation of Taylor expansion in MATLAB

Answer 1

[David Hill]

syms x
f=log(.7*x+.5);
x0=4.2857;
t=taylor(f,x,x0,'Order',2);
a= double(subs(t,6.42855))

a = 1.6813

Answer 2

[Torsten]

syms x
f = log(0.7*x+0.5);
x_0 = 4.2857;
t0 = taylor(f,x,x_0,'Order',2);
h = matlabFunction(t0);
h(6.42855)

ans = 1.6813

log(0.7*6.42855+0.5)

ans = 1.6094