Evaluating the area between two curves.

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Ejay Kasai 2011-9-12

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/15653-evaluating-the-area-between-two-curves

评论： Walter Roberson 2023-7-8

how to Evaluate the area between two curves using matlab? for example this one y=x^2 and y=2*x

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kalash vasaniya 2021-11-8

Find the area of the region bounded by the curves x=y^3 and x=y^2 in matlab

Walter Roberson 2021-11-8

在 MATLAB Online 中打开

syms x y

fimplicit([x == y^3, x == y^2], [-1 10])

@kalash vasaniya

Which of the two areas? The right-hand one is obviously unbounded, but your instructions do not say to do only the other area.

And please explain how your instructions will solve the question asked 10 years ago by Ejay Kasai ??

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回答（2 个）

Grzegorz Knor 2011-9-12

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/15653-evaluating-the-area-between-two-curves#answer_21244

在 MATLAB Online 中打开

http://www.mathworks.com/matlabcentral/answers/15551-how-to-compute-for-the-points-of-intersection-of-2-curves

http://www.mathworks.com/matlabcentral/answers/15550-how-to-create-a-matlab-program-computing-area-between-2-curves

In your case:

syms x
x0 = eval(solve('x^2 -2*x'));
x = linspace(x0(1),x0(2),100);
y1 = x.^2;
y2 = 2*x;
fill([x x(end:-1:1)],[y1 y2(end:-1:1)],'r')
hold on
plot(x,y1,x,y2,'LineWidth',2)
grid on
a = trapz(x,y2)-trapz(x,y1);

Instead of:

syms x
x0 = eval(solve('x^2 -2*x'));

You can use:

x0(1) = fzero('x.^2 -2*x',1);
x0(2) = fzero('x.^2 -2*x',1.5);

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Ejay Kasai 2011-9-13

i mean i need a code to evaluate the area between the two curves. i need to make a matlab program for that.

Walter Roberson 2011-9-13

The expression Grzegorz gave, a = trapz(x,y2)-trapz(x,y1) *is* the code to evaluate the area between the two curves. This is elementary calculus: the area between two curves is the difference between their integrals. trapz() calculates numeric integrals.

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