Right now, the equation I'm working on is $\displaystyle y''(t) - y(t) = t \mbox{sin}(t)$. Which form should I use for the particular solution? My guess is that the correct form should be $\displaystyle y_p(t) = (At + B)\mbox{sin}(t) + (Ct + D)\mbox{cos}(t)$. Is that the proper form or is it something else?