GIA'I PHU.O.NG TRNH
113)
Gia'i phu.o.ng trnh:
y” +y= 1sinxHD gia’i:Phu.o.ng trnh da.c tru.ng:
λ2
+ 1 = 0⇔λ=±iNTQ :
y=C1
cosx+C2
sinxTm nghi^e.m ri^eng da.ng:
y=α1
(x) cosx+α2
(x) sinxBang cach bi^en thi^en hang s^o
(α0
1
=−1(α1
=−xα0
1
cosx+α0
2
sinx= 0⇒α0
2
= cosxα2
= ln sinxα0
1
(−sinx) +α0
2
cosx= 1V^a.y nghi^e.m t^o'ng quat:
y=C1
cosx+C2
sinx−xcosx+ sinxln sinx