||'''Book'''|| Advanced Engineering Mathematics ||
 ||'''Author'''|| Erwin Kreyszig ||
 ||'''Edition'''|| 8th Edition ||

/* code_begins */

{{{
 x=var('x')#2
y=function('y',x)
DE=diff(y,x,x)+9*y-sec(3*x)
desolve(DE,[y,x])

}}}

/* code_ends */

 * '''Solution by''': 
   * <Manjusha S. Joshi>, <Lecturee>, <Bhasakracharya Institute of Mathematics, Pune>