cantilever beam matlab equation solve

syms x

k=25

eqn = 1+ 1/cos(k*x)*cosh(k*x)-11.4*k*x*(tan(k*x)-tanh(k*x))/84.9684 == 0;

S = solve(eqn,x,"Real",true);

i want to solve that equation. that equation is about cantilever beam vibration.

i want 4 plus solution in small order . however i can get only 1 solution (25)

Answer 1

[Sam Chak]

Hi @영범 곽

The function seems to have no real roots. Please check the trigonometric function again if something is missed.

k = 25;
f = @(x) 1 + 1./cos(k*x).*cosh(k*x) - 11.4*k*x.*(tan(k*x) - tanh(k*x))/84.9684;
fplot(f, [-0.1 0.1]), ylim([-20 20])