How do I integrate a combined function?

For my own script, I need to combine several functions and finally calculate the integral of the lot. To simplify it, I made a simple problem with the same error:

"Input function must return 'double' or 'single' values. Found 'function_handle'.". The actual code is much larger, has more parameters and because of the size of the function I prefer multiple seperate functions.

a = @(x) x;
b = @(x) a*cos(x);

C = integral(@(x) b,0,5);

I understand the @(x) is not the right way for using the integral-function, because it should have double or single values, as stated in the error. But in what way should I handle this problem to get the right answer out this simple example? (ans = -5,51...)

Answer 1

[Star Strider]

Since ‘a’ is a function of ‘x’, call it as a function.

Try this:

a = @(x) x;
b = @(x) a(x).*cos(x);
C = integral(b,0,5)

returning:

C =
         -5.51095918785247         

Also, since ‘b’ already exists as a function, the extra function handle is not necessary (unless it is a function of several variables, and only integrating with respect to one). In that event, it is still necessary to refer to it as a function:

C = integral(@(x)b(x),0,5)

[Jasper Kregting]

I tried this solution within my own script and it works! Thanks a lot.

[Star Strider]

As always, my pleasure!