Spot the Mistake in Equation

[strokebow]

Hi guys,

Please can someone look at this working (see attached).

The equation in question is [43]. It is highlighted with a red border.

The numerical answers in the pdf are correct and have been verified against published material.

That being said, I believe there must be a problem with equation [43] as I am not getting the same answers. I don't know how the algebra was simplified etc. to get to [43].

I have inputted [43] as it is in MATLAB and get incorrect results:

function [y] = inf_res_hex_odd(x,y,m,n)
y = ((1)/(4*(pi^2)))*((3-2*cos(y).*cos(m*x+n*y)-cos((m-1)*x+n*y))./(4-cos(y).*(cos(y)+cos(x))));
end

Example:

>> real((quad2d(@(x,y)inf_res_hex_odd(x,y,1,0),-pi,pi,-pi,pi)))

ans =

0.5422

There are 2 possibilities:
1) I made a mistake in my MATLAB function, or,
2) There is a mistake/typo in [43]

If anyone can offer any help with this I would be really appreciative.

Thanks

 

[strokebow]

No takers?

I've been staring at this bad boy for some time now... can't manage to find the problem.

any help/suggestions would be much appreciated... :-)

 

[mathman]

The material is too cryptic to respond to.

 

[Matt Benesi]

Don't expect people to look up MatLab syntax and command(s).

Type the equation in Latex so people can see it. What variables do you put in for x,y,m, and n? (I (and maybe others) don't know MatLab syntax/command(s) so don't know what the (x,y,1,0... -pi,pi,-pi,pi) stuff means, although it looks like ranges of evaluation)

In addition, your formatting was sloppy/lazy: there are more ))) on the one side of 1/4pi^2 than there are on the other. How is someone supposed to understand what you actually want?

Something like:
$$f(x,y,m,n)=\frac {\frac {1} {4 \times \pi^2} \times \left ( 3-2 \times \cos{y} \right) \times \cos \left( m \times x + n \times y \right ) - \cos \left ( \left (m-1 \right ) \times x + n \times y \right)} {\left ( 4-\cos{y} \right ) \times \left (\cos{y} + \cos{x} \right ) }$$

 

[CellCoree]

Hi there,

Thank you for bringing this to our attention. After reviewing the attached working and the equation in question [43], I believe there is a typo in the equation. The denominator should be (4-cos(y)*(cos(y)+cos(x))) instead of (4-cos(y)*(cos(y)+cos(x))). This small error could be causing the incorrect results in your MATLAB function.

I would recommend double checking the rest of your function and equations to ensure there are no other typos or mistakes. If the issue persists, it might be helpful to consult with a colleague or supervisor for a second opinion.

I hope this helps and good luck with your research.