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: Is this DE nonlinear?

  1. Jan 15, 2009 #1
    Is this DE nonlinear????

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

    Determine the order and if this equation is Linear or Nonlinear.

    3(d4x/dt4) + 4(dx/dt) + 9x = 3cos(3t)

    The d4x is a forth order derivative. Sorry for the messiness.

    Ok, this is a 4th order DE. I think it is nonlinear because of the two products (multiplying 4 time the derivative and 4 times the other derivative).

    Also, the 3cos(3t) has no bearing on this because t is independent right? If the t was a y, that would cause nonlinearness.

    Am I right on all this?
  2. jcsd
  3. Jan 15, 2009 #2
    Re: Is this DE nonlinear????

    Define linear DE
  4. Jan 15, 2009 #3
    Re: Is this DE nonlinear????

    A linear differential equation is one in which the derivative has no function of itself (e^y, cosy, ln(y)). That is if I was differentiating with respect to y.
  5. Jan 15, 2009 #4
  6. Jan 15, 2009 #5
    Re: Is this DE nonlinear????

    Ok.. So my equation is Linear. But you cannot have, 3a*y'. This product will make it nonlinear.
  7. Jan 15, 2009 #6
    Re: Is this DE nonlinear????

    What's a?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook