a) Find the Laplace transform of tet sin 3t

  • matematika

    Subject:

    Math
  • Author:

    laurel
  • Created:

    1 year ago

Answers 1

Let's find the Laplace transform of tsin3ttsin⁡3t.

Let f(t)=tsin3t.f(t)=tsin⁡3t. Then f(0)=0.f(0)=0.

Deriving we have

f′(t)=sin3t+3tcos3tf′(t)=sin⁡3t+3tcos⁡3t. Then f′(0)=0f′(0)=0.

calculating f′′(t)f″(t), we have

f′′(t)=3cos3t+3tcos3t−9tsin3tf′′(t)=6cos3t−9tsin3t.f″(t)=3cos⁡3t+3tcos⁡3t−9tsin⁡3tf″(t)=6cos⁡3t−9tsin⁡3t.

So taking the transform we have

L{f′′(t)}=6L{cos3t}−9L{tsin3t}.L{f″(t)}=6L{cos⁡3t}−9L{tsin⁡3t}.

But L{f′′(t)}=s2L{f(t)}L{f″(t)}=s2L{f(t)} and L{cos3t}=ss2+9.L{cos⁡3t}=ss2+9.

So we have

s2L{tsin3t}=6ss2+9−9L{tsin3t}.s2L{tsin⁡3t}=6ss2+9−9L{tsin⁡3t}.

Solving we have

s2L{tsin3t}+9L{tsin

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