How can I fix this error?

I had a code like this:

clear all, close all

f = @(x)(4/(1+x^2));

a = 0;

b = 1;

F = @(x)(-8x/((1+x^2)^2)); % antiderivative of f

ref = F(b) - F(a);

n = 2;

x = linspace(a,b,n+1);

h = (b-a)/n;

then in the command part, it shows:

File: assignment3_question2b.m Line: 7 Column: 12

Invalid expression. Check for missing multiplication operator, missing or unbalanced

delimiters, or other syntax error. To construct matrices, use brackets instead of parentheses.

How can i fix this?

Answer 1

[David Hill]

f = @(x)4./(1+x.^2) 

f = function_handle with value:
    @(x)4./(1+x.^2)

a = 0;
b = 1;
F = @(x)-8*x./(1+x.^2).^2 % antiderivative of f

F = function_handle with value:
    @(x)-8*x./(1+x.^2).^2

ref = F(b) - F(a);
n = 2; 
x = linspace(a,b,n+1); 
h = (b-a)/n; 

[Wenchen Liu]

clear all, close all

f = @(x)4./(1+x.^2);

a = 0;

b = 1;

F = @(x)-8*x.(1+x.^2).^2; % antiderivative of f

ref = F(b) - F(a);

n = 2;

x = linspace(a,b,n+1);

h = (b-a)/n;

i have fixed the questions, but in the command it still shows:

Argument to dynamic structure reference must evaluate to a valid field name.

Error in assignment3_question2b (line 7)

F = @(x)-8*x.(1+x.^2).^2 % antiderivative of f

Error in assignment3_question2b (line 8)

ref = F(b) - F(a);

[Torsten]

F = @(x)-8*x.*(1+x.^2).^2; % antiderivative of f

instead of

F = @(x)-8*x.(1+x.^2).^2; % antiderivative of f

But the antiderivative of f is of course

F = @(x) 4*atan(x)