solve some integrals using trapezoidal rule and a matlab built-in function and to represent the original function in a graph

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DDD 2015-5-10

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https://ww2.mathworks.cn/matlabcentral/answers/215964-solve-some-integrals-using-trapezoidal-rule-and-a-matlab-built-in-function-and-to-represent-the-orig

回答： Walter Roberson 2015-5-10

It is asked to solve some integrals using trapezoidal rule and a matlab built-in function and to represent the original function in a graph.

Here is the code i did:

    f1=@(x) (x.^2+1)/((x+2).*sqrt(1-2*x));
    a=0; b=.5;
    N=100;
    figure()
    fplot(f1,[a,b])
    grid on
    res_trap=trapezios(f1,a,b,N);
    res_matlab=integral(f1,a,b);
    f1=@(x)((sin(x))/x.^2);
    figure()
    fplot(f1,[0,10])
    grid on
    a=1; b=inf;
    N=10;
    res_trap=trapezios(f1,a,b,N);
    res_matlab=int(f1,1,inf);
    syms t
    f1=@(x,y)x.^2*y;
    a=0; b=y; c=0; d=1;
    eixox=@(y)y;
    ezsurf(f1,0,eixox(),0,1)
    res_trap=trapezios(f2,c,d,N);
    res_matlab=int2(f1,0,1,0);

Here is the trapezoidal integration function I did:

function It=trapezios(f,a,b,N)
h=(b-a)/N;
It=0;
for k=1:(N-1)
     x=a+h*k;
     It=It+feval(f,x);
  end
It=h*(f(a)+f(b))/2+h*It;
end

When i run the code several errors occur. What is wrong?

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Image Analyst 2015-5-10

You might get answers faster if you told people what the errors were rather than forcing them to copy the code, switch to MATLAB, paste the code, and then run it.

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