1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Help with solving a IH equation

  1. Oct 24, 2009 #1
    1. The problem statement, all variables and given/known data

    d2i/dt2 + 6di/dt + 25i = -292sin4t

    2. Relevant equations

    3. The attempt at a solution

    i got a solution of
    Ae^(-3t)cos4t + Be^(-3t)sin4t + 292/9(cos4t) + 146/9(sin4t)
    want to know if im right
    Last edited: Oct 24, 2009
  2. jcsd
  3. Oct 24, 2009 #2


    Staff: Mentor

    Your solution looks reasonable. Your solution can be divided into two parts: the solution to the homogeneous equation i'' + 6i' + 25i = 0, and the particular solution to the nonhomogeneous equation you have.

    So your general solution is i(t) = ih(t) + ip(t), where ih(t) consists of the first two terms of your solution, and ip(t) consists of the last two terms.

    Your homogeneous solution checks with what I got. To confirm that your general solution is correct, all you need to do is check that your particular solution actually works.

    From ip(t) = (292/9)cos4t + (146/9)sin4t, calculate ip' and ip''. If ip'' + 6ip' + 25ip equals -292sin4t, your solution is correct.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook