from Vibration Modes of an Elliptic Membrane by Howard Wilson
Elliptic membrane frequencies and mode shapes are analyzed using Mathieu functions.

w=asymtroe(type,a,b,m,k)
function w=asymtroe(type,a,b,m,k)
% w=asymtroe(type,a,b,m,k) computes
% approximate zeros of Mc1(z,n,q)
% using an asymptotic formula

%      HBW 12/01/04
r=b/a; M=length(m); K=length(k);
m=m(:)*ones(1,K); k=ones(M,1)*k(:)';
if type==1 % even modes
  w=((k-1/2)*pi+(m+1/2)*r+...
     (m.^2+m+1)./(4*k-2)*(r^2/pi))/b;
else       % odd modes
  w=(k*pi+(m-1/2)*r+...
    ((m-1).^2+m)./(4*k)*(r^2/pi))/b; 
end    

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