Math 246 Syllabus

BD indicates sections from the textbook (Boyce & DiPrima), M indicates sections from Differential Equations with Matlab.

Clarification of classification of Critical Points

Table 9.3.1 on page 484 in Boyce/diPrima gives types of critical points of almost linear systems. In the "borderline cases" actually more general types of critical points can appear:

r1 = r2 > 0 or r1 = r2 < 0
the type of the almost linear system should be more general types of N, SpP (which can look different from the nodes and spiral points for linear systems) . In this case the statement below the table (that the slopes are the same as for the linear equation) is not always true.
r1 = imu , r2 = -imu with nonzero mu
the type of the almost linear system should be C, SpP or other.

In these cases even very near the critical point the trajectories of the nonlinear system can be very different from those of the linear system.

Here is a correct table. One can construct examples where ``other'' types than the ones in table 9.3.1 occur.