2.1 Ordinary 2nd Order Linear Differential Equations
  2.1.1 Origin of ODEs
  2.1.2 Definitions
  2.1.3 How to Solve Them
 2.2 ODE with constant coefficients I
  2.2.1 Undamped oscillator
  2.2.2 Initial Value Problem
  2.2.3 Exponential
  2.2.4 Summary
 2.3 2nd order ODE with constant coefficients II
  2.3.1 Positive discriminant
  2.3.2 negative discriminant
  2.3.3 The Marginal Case
  2.3.4 Summary
 2.4 Inhomogeneous Equations
  2.4.1 Solution to inhomogeneous equations
 2.5 * Green’s function approach
  2.5.1 * Initial Conditions for the Homogeneous Case
  2.5.2 * The Inhomogeneous Case: Effect of the External Force