Evaluating the area between two curves.

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Ejay Kasai
Ejay Kasai 2011 年 9 月 12 日
コメント済み: Walter Roberson 2023 年 7 月 8 日
how to Evaluate the area between two curves using matlab? for example this one y=x^2 and y=2*x
  2 件のコメント
kalash vasaniya
kalash vasaniya 2021 年 11 月 8 日
Find the area of the region bounded by the curves x=y^3 and x=y^2 in matlab
Walter Roberson
Walter Roberson 2021 年 11 月 8 日
syms x y
fimplicit([x == y^3, x == y^2], [-1 10])
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 件)

Grzegorz Knor
Grzegorz Knor 2011 年 9 月 12 日
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);
  6 件のコメント
Ejay Kasai
Ejay Kasai 2011 年 9 月 13 日
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
Walter Roberson 2011 年 9 月 13 日
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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Shyam babu
Shyam babu 2023 年 7 月 8 日
find the area included between the curves y^2=4*x & x^2=4*y
  1 件のコメント
Walter Roberson
Walter Roberson 2023 年 7 月 8 日
I do not seem to understand how this would solve the question posted by @Ejay Kasai ??

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