State Equations: State determined system is a system in which the time derivatives of the variables describing the state (the state variables) are determined by the current state and the values of the inputs. Set of coupled, first order differential equations. One for each independent energy storage element. Particularly useful for non-linear systems.

For sinusoidal steady state analysis, we can use s-> jw For sinusoidal steady state analysis, we can use s-> jw. This assumes that any transient response has died out. This would be appropriate for analysis of the frequency response of a filter, for example.

x = x0(coswt + )