Can you post solved problems using these conditions? We're on the Advanced Engineering Mathematics and reviewing our Differential Equations. My professor only introduces this topic and didn't went deeper. I'm troubled about the sign convention, e.g.:(adsbygoogle = window.adsbygoogle || []).push({});

(D^2-9)y=-sin4x

(D^2-a^2)y=sinbx

yp=-sinbx/(a^2+b^2)

a=3, b=4

yp=sin4x/(3^2+4^2)

yp=sin4x/25

how does yp became positive? What are the formulae used... also for cosine condition?

Thanks for your help!

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: DE: Inspection for R(x)=sinx or cosx

**Physics Forums | Science Articles, Homework Help, Discussion**