how can I solve transcendental equation?

I want to solve the given equation in matlab to find the value of beta but getting error. I am posting the code and error below.

Thanks in advance.

n1=1.77;
n2=1.45;
d=1e-6;
lambda = 1e-6;
ko = 2*pi/lambda;
A=(ko*n1)^2;
B=(ko*n2)^2;
syms beta;
s = 'sqrt(A-beta^2)*(d/2)*tan(sqrt(A-beta^2)*d/2)=sqrt(beta^2-B)*(d/2)';
solve (s);

Error:

Error using solve>processString (line 337) ' sqrt(A-beta^2)*(d/2)*tan(sqrt(A-beta^2)*d/2)=sqrt(beta^2-B)*(d/2) ' is not a valid expression or equation.

Error in solve>getEqns (line 267) eqns = processString(eqns, v, vc);

Error in solve (line 150) [eqns,vars,options] = getEqns(varargin{:});

Error in transcendetal (line 9) solve (s);

Answer 1

[Walter Roberson]

s = sqrt(A-beta^2)*(d/2)*tan(sqrt(A-beta^2)*d/2) - sqrt(beta^2-B)*(d/2);