Apr 15, 2002 ------------ - Introduction to differential equations - closed-form solution versus numerical solutions - Sample problems and solutions - x' = x (x = ce^t) - x' = -x (x = ce^(-t)) - x'' = x (x = ce^t + de^(-t)) - x'' = -x (x = c sin(t) + d cos(t)) - x' = 2x (x = ce^(2t)) - In general, there exist a family of solutions - if initial value is given, then we can pin point a specific function - Initial value problems - e.g., x' = 2x, x(0) = 15 - answer here is x = 15 e^(2t) - Solving differential equations by Taylor series - first-order approximations (Euler method) - Taylor series methods of higher orders - how to get expression for higher order derivatives? - Causes of errors in differential equations Apr 17, 2002 ------------ - Causes of errors in differential equations (contd.) - roundoff error - truncation error - error in recording values (perturbations of initial value) - Better methods - Runge-Kutta methods (e.g., order 2) Apr 19, 2002 ------------ - Stability of differential equations to numerical solution - convergence of solution curves - divergence of solution curves - sufficient tests for stability - Solving a system of ODEs - coupled - uncoupled - Solving higher-order ODEs - introduce new variables to reduce to first-order system