# Method of Undetermined Coef.

1. Sep 30, 2008

### strawberrysk8

1. The problem statement, all variables and given/known data

Find particular solution for
y''+2y'+5y = 4(e^-t)cos2t

2. Relevant equations

y.c = C(e^-t)cos2t + C(e^-t)sin2t

3. The attempt at a solution

y.p (particular solution) = At(e^-t)cos2t + Bt(e^-t)sin2t does not work! Help please!

2. Sep 30, 2008

### gabbagabbahey

Are you sure your $y_p$ doesn't work? Why don't you show us what you're getting when you plug it into the ODE.

Last edited: Sep 30, 2008
3. Sep 30, 2008

### strawberrysk8

reply oh i figured it out. thank you!