Non-Homogeneous Linear Differential Equation (The Method of Undetermined Coefficients). Solve the

Stacie Worsley

Stacie Worsley

Answered question

2022-01-02

Non-Homogeneous Linear Differential Equation (The Method of Undetermined Coefficients).
Solve the equation (D+1)y=sinx

Answer & Explanation

Alex Sheppard

Alex Sheppard

Beginner2022-01-03Added 36 answers

(D2+1)y=sinx
m2+1=0
m2=1
m=±i
C.f=C1cosx+C2sinx
yt=x(acosx+bsinx) (1)
ytyt=sinx (2)
equation (1) D.w.r. to x
yt=x(asinx+bcosx)+(acosx+bsinx)
again D.w.r. to x
ytx(acosxbsinx)+(asinx+vcosx)±asinx+bcosx
=x(acosxbsinx)2asinx+2bcosx (3)
eq (1) and eq (3) put in eq (2)
x(acosxbsinx)2asinx+2bcosx+x(cosx+bsinx)=sinx
equat the coefficient
2asinx+2bcosx=sinx
2a=1
a=12
2b=0
b=0
P.I is yt=12xcosx
y=c1cosx+c2sinx12xsinx
Alex Sheppard

Alex Sheppard

Beginner2022-01-04Added 36 answers

Here A.E. is
m2+1=0 and its roots are m=±i
Hence C.F.=C1cosx+C2sinx
Note that sin x is common in the C.F. and the R.H.S. of the given equation. (± i is the root of the A.E.)
Therefore P.I. is y the form yp=x(acosx+bsinx) ...(1)
Since ± i is root of the A.E.
We have to find a and b such that yp+yp=sinx ...(2)
From Eqn. (1) yp=x(asinx+bcosx)+(acosx+bsinx)
yp=x(acosxbsinx)+(asinx+bcosx)asinx+bcosx
=x(acosxbsinx)2asinx+2bcosx
Then the given equation reduces to using the Eqn. (1) x(acosxbsinx)2asinx+2bcosx+x(acosx+bsinx)=sinx
Equating the coefficients, we get
i.e.,2asinx+2bcosx=sinx
2a=1,2b=0
a=12,b=0
Thus P.I. is yp=12xcosx
y=C.F.+P.I.
=C1cosx+C2sinx12xsinx.
karton

karton

Expert2022-01-09Added 613 answers

Given: (D2+1)y=sinxP.I.=1D2+1sinx=11+1sinx=x12Dsinx=x2sinxdx=x2(cosx)P.I.=xcosx2

Do you have a similar question?

Recalculate according to your conditions!

New Questions in Differential Equations

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?