DOUBLE cannot convert the input expression into a double array?

Hi everybody,

I want to calculate a problem about Taylor series from a book but an error message occurred as follows:

Thank you from now.

The following error occurred converting from sym to double:
Error using symengine (line 59)
DOUBLE cannot convert the input expression into a double array.
If the input expression contains a symbolic variable, use VPA.

Error in example_four3 (line 35)
    sol(i+1) = sol(i+1) + (diff(f,(i+1))) * (h^(i+1)/factorial(i+1));

Here is my code:

clc;
clear;

anglout = radtodeg(pi);

true_value = cos(pi/3);

h = pi/3-pi/4;
n = 6; 

syms x
f = cos(x);

sol(1) = cos(pi/4);
for i = 0:n
    sol(i+1) = sol(i+1) + (diff(f,(i+1))) * (h^(i+1)/factorial(i+1));
    sol(1) = sol(i);
end

Answer 1

[Stephan]

clc;
clear;
anglout = rad2deg(pi);
true_value = cos(pi/3);
h = pi/3-pi/4;
n = 6; 
syms f(x) op(x)
f(x) = cos(x);
sol = zeros(1,7);
sol = cos(pi/4);
for i = 0:n
    op(x) = (diff(f,x,(i+1)));
    sol = double(sol + op(i+1) * (h^(i+1)/factorial(i+1)));
end