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

/* code_begins */

{{{
x=var('x')
y=function('y',x)
deq1=diff(y,x)+4*y-cos(x)==0
r=desolve(deq1,[y,x],y)
show(r.simplify_full())

.}}}

/* code_ends */

 * '''Solution by''': 
   * A.sai kiran reddy ,student,snist