Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Cauchy Method/ UC set OR Variation of Param?

  1. Mar 6, 2012 #1
    Hello new to this forum , Was solving some Diff eq problems and iam getting two different answers using two methods, ok the problem is i=primes (x^2)(y^ii)+(x)(y^i)+y=4sin(lnx)
    This is cauchy method, When i use variation of parameters i get a long answer with impossible integrals and when i use Undetermined coefficients i also get an answer, Not sure witch is correct i also understand that Uc method cant be used with tanx, secx, lnx, but in this case that there is a sin in there iam not sure. Thanks
  2. jcsd
  3. Mar 7, 2012 #2


    User Avatar
    Science Advisor

    Please show what you did and what answer you got.

    (Note that the substution u= ln(x) turns this into the differential equation with constant coefficients, y''+ y= ln(u) where the primes now indicate differentiation with respect to u.)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook