how do I solve symbolic eigenvalue?

this is my code:

syms ei  l
h=l/4;
k=(2*ei/h^3)*[6 -3*h -6 -3*h; -3*h 2*h^2 3*h h^2; -6 3*h 6 3*h; -3*h h^2 3*h 2*h^2];
m=(1/(30*h))*[36 -3*h -36 -3*h; -3*h 4*h^2 3*h -h^2; -36 3*h 36 3*h; -3*h -h^2 3*h 4*h^2];
K(1,:)=[];
K(:,1)=[];
M(1,:)=[];
M(:,1)=[];
[v,d]=eig(K,M)

i recieved this error:

Error using sym/eig

Too many input arguments.

what should i do?

[Star Strider]

In the Symbolic Math Toolbox eig function, there is only one argument.

syms ei  l
h=l/4;
k=(2*ei/h^3)*[6 -3*h -6 -3*h; -3*h 2*h^2 3*h h^2; -6 3*h 6 3*h; -3*h h^2 3*h 2*h^2];
m=(1/(30*h))*[36 -3*h -36 -3*h; -3*h 4*h^2 3*h -h^2; -36 3*h 36 3*h; -3*h -h^2 3*h 4*h^2];
% K(1,:)=[];
% K(:,1)=[];
% M(1,:)=[];
% M(:,1)=[];
[v,d]=eig(k)

v = 

d = 

.

[Walter Roberson]

Right, symbolic eig() does not support generalized eigenvalues.

Answer 1

[VBBV]

I presume you need to compute the inverse of mass matrix , m, for a 4 x 4 stiffness matrix , before finding the Eigen solution. However, check the equations if they are correct

syms ei  l
h=l/4;
k=(2*ei/h^3)*[6 -3*h -6 -3*h; -3*h 2*h^2 3*h h^2; -6 3*h 6 3*h; -3*h h^2 3*h 2*h^2]

k = 

m=(1/(30*h))*[36 -3*h -36 -3*h; -3*h 4*h^2 3*h -h^2; -36 3*h 36 3*h; -3*h -h^2 3*h 4*h^2]

m = 

V = m\k  % Take the inverse of matrix m 

Warning: Solution is not unique because the system is rank-deficient.

V = 

[v,d]=eig(V)  % only one argument

v = 

d = 

Answer 2

[Torsten]

syms ei  l
h=l/4;
k=(2*ei/h^3)*[6 -3*h -6 -3*h; -3*h 2*h^2 3*h h^2; -6 3*h 6 3*h; -3*h h^2 3*h 2*h^2];
m=(1/(30*h))*[36 -3*h -36 -3*h; -3*h 4*h^2 3*h -h^2; -36 3*h 36 3*h; -3*h -h^2 3*h 4*h^2];
k(1,:)=[];
k(:,1)=[];
m(1,:)=[];
m(:,1)=[];
[v,d]=eig(inv(m)*k)

v = 

d =