Solving MATLAB Plotting Error for x(t) Function

[farhadd]

Hello,

I've written a piece of code in MATLAB, to depict the function x(t)

I have the Fourier coefficients of this function as following:

a(k) = 1/(k.*pi)^2

where k is even and otherwise a(k) = 0.

also we know that x(t+5) = x(t)

my code is :

function [zaribX] = Ak(k)  

    if ~((mod(k,2) == 1) || k==0)  
        zaribX=1./(k.*pi).^2; 
    else zaribX=0;
    end
return;
end

function [x] = FunctionX(Kmax,t)
x = 0;
	for m = 0:Kmax
		f = 2 .* abs(Ak(m)) .* cos( m .* ((2.*pi)./5) .* t + angle(Ak(m)));
		x = x+f;
	end
return;
end

problem is, when MATLAB plots the function, it appears to have a period of 2.5 , and not 5. Could anyone help me see what's going wrong? Thanks a lot.

 

[NateD]

The problem is likely coming from the angle of the Fourier coefficients. In your code, you are computing the angle of each coefficient as angle(Ak(m)). However, this will yield a value of zero for all m, resulting in a period of 2.5. You should instead use a different value for the angle for each Fourier coefficient - for example, 0 for m=0 and pi/2 for m>0. This should result in a period of 5 for the function.