Kindly help me integrate this function.

2014 5 11
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更新时间：2014 5 11
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I am trying to integrate the following expression using 'quad' fuction but MATLAB is giving errors, kindly help me with the code. Code starts below:
f= @(x) ((sin(x))^2)/(((sin(x))^2)+(7));
% a, the lower limit
a= 0 ;
% b, the upper limit
b= pi/2 ;
answer=quad(f,a,b);
%%% Code ends
MATLAB gives following error:
??? Error using ==> mpower Inputs must be a scalar and a square matrix.
Error in ==> @(theta)((sin(theta))^2)/(((sin(theta))^2)+(7))
Error in ==> quad at 77 y = f(x, varargin{:});
Kindly help.

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Star Strider
Star Strider 2014-5-11

2 个投票

You need to vectorize your code.
This works:
f= @(x) ((sin(x)).^2)./(((sin(x)).^2)+(7));
a= 0 ;
b= pi/2 ;
answer=quad(f,a,b);
produces:
answer =
101.4509e-003

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Furqan Haider
Furqan Haider 2014-5-11
Bundle of thanks Star Strider, i am facing an other issue. In the function statement, instead of '7' I have a vector h=1:0.02:10 i.e.
f= @(x) ((sin(x)).^2)./(((sin(x)).^2)+(h));
I wish to integrate my function for all the values of vector 'h'. Can u help me out ?
Star Strider
Star Strider 2014-5-11
My pleasure!
Here is your integral over your vector h:
h=1:0.02:10;
a= 0 ;
b= pi/2 ;
for k1 = 1:length(h)
H = h(k1);
f= @(x) ((sin(x)).^2)./(((sin(x)).^2)+H);
answer(k1)=quad(f,a,b);
end
Your answer variable is now a vector of length(h). When I plotted it, it looked like a smooth decaying exponential.
Furqan Haider
Furqan Haider 2014-5-11
Thank u again, I got what was required.
Best regards.

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