Singular matrix error when code is running?

• When I run this code I am getting a singular matrix error and all the values of A\alpha show up as NaN. Anyone have any idea how to fix this? I am not sure what is wrong. The code runs the output just shows up as NaN.

b=6;    % Wing span
  n=7;
    % number of sections of wing
  Type=2; % Type 1 for elliptical wing type 2 for other

    c=1;

    theta0=linspace(0,pi,n); % theta values for wing span
    y0=-b/2*cos(theta0);     % Points along wing
    S=b*c;                  % Wing area

    c=transpose(interp1([-b/2,0,b/2],[c,c,c],y0)');
    AR=b^2/S;                                  % Aspect Ratio
    Vinf=36; rho=0.125;                         % speed and density of the air

    alpha0=0;                                   % alpha_zero_lift  (in degrees)
    alpha0=alpha0*ones(n,1)/180*pi;

    Clalpha=2*pi;                % in rad^-1
    Clalpha=Clalpha*ones(n,1);  % lift gradient of each wing section

    alphar=2;                   % angle of attack of the wing root, in degrees
                                % (it's the reference angle of the wing)

    e=1*ones(n,1);              % twist of each wing section, in degrees

    % --------------------------------------------------------------------
    % END OF THE INPUT SECTION

    alpha=(alphar-e)/180*pi
          % angle of attack of each section (in degrees)

    % I build the system A*An=Anoto of n-2 equation, and my PC solve it!
    for i=1:n;
      i;
      for j=1:n,
        j;
     A(i,j)=4*b*sin((j)*theta0(i))/Clalpha(i)/c(i)+(j)*sin((j)*theta0(i))/sin(theta0(i));
      end;
    end;
    A\alpha

Answer 1

[Roger Stafford]

In your expression for A(i,j) you divide by sin(theta0(i)) which is zero at three places as you have defined it. That will give you NaNs all over the place. Why do you want to make such a division?