ω0 is called the natural frequency of the system, while ζ is the damping ratio. With these 2 parameters we can rearrange equation 3.2 again:
Equation 3.5 To solve this differential equation we assume that, so and. When we substitute this in equation 3.5 we get:
Equation 3.5
, so 
and
. When we substitute this in equation 3.5 we get: