Hi A. Hossain
Try this:
clear; clc;
syms w d k
d=100
g=10
for w=0:0.1:20
fprintf('----- w = %f -----\n', w);
eq=w.^2==g*k*tanh(k*d)
vpasolve(eq)
fprintf('\n\n');
end
Of Course, it does not provide an analytical solution, but a numerical one.