To find the inverse Laplace transform of the given function, we first perform partial fraction decomposition.
The function is:
F(s)=s2(s+1)(s2+9)1
Step 1: Partial Fraction Decomposition
We set up the partial fraction decomposition as follows:
s2(s+1)(s2+9)1=sA+s2B+s+1C+s2+9Ds+E
Multiply both sides by s2(s+1)(s2+9):
1=As(s+1)(s2+9)+B(s+1)(s2+9)+Cs2(s2+9)+(Ds+E)s2(s+1)
To find the coefficients, we can substitute specific values for s:
- Set s=0:
1=A(0)+B(0+1)(02+9)+C(0)+(D(0)+E)(0)
1=B(1)(9)⟹9B=1⟹B=91
- Set s=−1:
1=A(−1)(−1+1)((−1)2+9)+B(−1+1)((−1)2+9)+C(−1)2((−1)2+9)+(D(−1)+E)(−1)2(−1+1)
1=A(0)+B(0)+C(1)(1+9)+(D(−1)+E)(0)
1=10C⟹C=101
Now, expand the equation and equate coefficients of powers of s:
1=A(s4+s3+9s2+9s)+B(s3+s2+9s+9)+C(s4+9s2)+(Ds+E)(s3+s2)
1=A(s4+s3+9s2+9s)+B(s3+s2+9s+9)+C(s4+9s2)+(Ds4+Ds3+Es3+Es2)
1=(A+C+D)s4+(A+B+D+E)s3+(9A+B+9C+E)s2+(9A+9B)s+9B
Equating coefficients:
- Constant term: 1=9B. This confirms B=91.
- Coefficient of s: 0=9A+9B
Substitute B=91:
0=9A+9(91)⟹0=9A+1⟹A=−91
- Coefficient of s4: 0=A+C+D
Substitute A=−91 and C=101:
0=−91+101+D⟹D=91−101=9010−9=901