I understand how to analyse a system of equations like
$x'(t) = f(x,y)$
$y'(t) = g(x,y)$
set $x'$ and $y'$ to zero and find the fixed points etc, and find the stability.
What Im am not sure of is analyzing an equation of the form
$x'''(t) + x''(t) + x'(t) + a sin(x) = 0$
I want to find the stability and hopf bifurcation parameter $a_h$ for the above system.