Trapezoidal rule for loop

Question

NIMA RAHMANI MEHDIABADI 2019-4-29

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/459069-trapezoidal-rule-for-loop

评论： Katerin 2021-3-31

So i have done the calculation for only one value of n = 200. The code that i have written is :

f = @(x)6*(cos(x/2)) .* (sin(x/2)).^2;   % Defining given function
a = 0; % lower limit
b = pi; % upper limit
n = 200;   % Number of intervals
h = (b-a)/n;   % Width of each interval
s = 1/2 * (f(a) + f(b));   % Summation value
% make for loops to calculate values between the intervals
for i = 1 : n-1
    s = s + f(a + i*h);
end
A = h * s;   % The calcuated sum of all intervals
format long   % Make the outcome to be in long format
disp(A)   % Display the outcome

However now that i'm trying to make the loop for values of n = 20 , 50 , 100 , 150, 400. But im struggling to adjust the above code. any help is very appreciated.

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Answer 1

Geoff Hayes 2019-4-29

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https://ww2.mathworks.cn/matlabcentral/answers/459069-trapezoidal-rule-for-loop#answer_372702

在 MATLAB Online 中打开

Nima - perhaps try

for n = [20,50,100,150,400]
    f = @(x)6*(cos(x/2)) .* (sin(x/2)).^2;   % Defining given function
    a = 0; % lower limit
    b = pi; % upper limit
    h = (b-a)/n;   % Width of each interval
    s = 1/2 * (f(a) + f(b));   % Summation value
    % make for loops to calculate values between the intervals
    for i = 1 : n-1
        s = s + f(a + i*h);
    end
    A = h * s;   % The calcuated sum of all intervals
    format long   % Make the outcome to be in long format
    fprintf('n = %d value=%f\n', n, A);   % Display the outcome
end