Find the Laplace transforms of the functions given in problem f(t)=sin pi t text{ if } 2leq tleq3 , f(t)=0 text{ if } t<2 text{ or if } t>3

lwfrgin

lwfrgin

Answered question

2020-11-23

Calculate the Laplace transforms for the given functions.
f(t)=sinπt if 2t3, 
f(t)=0 if t<2 or if t>3

Answer & Explanation

ensojadasH

ensojadasH

Skilled2020-11-24Added 100 answers

Step 1 
Given function is 
{sinπt2t3023
The Laplace transform of function f(t) is defined by 
L[f(t)]=0estf(t)dt 
=02estf(t)dt+23estf(t)dt+3estf(t)dt 
=23estf(t)dt{f(t)=0,2<t or t>3} 
=23estsin(πt)dt 
Step 2 
Now, we firstly evaluate the indefinite integral by parts. 
I=estsin(πt)dt=sin(πt)estdt((ddt)sin(πt)estdt)dt 
I=estssin(πt)πcos(πt)(ests)dt 
I=estssin(πt)+πsestcos(πt)dt 
Again , we integrate by parts. 
I=estssin(πt)+πs[cos(πt)estdt(ddtcosπtestdt)dt] 
I=estssin(πt)+πs[estscos(πt)(πsin(πt))(ests)dt] 
I=estssin(πt)+πs[estscos(πt)πsestsin(πt)dt] 
I=estssin(πt)πests2cos(πt)π2s2I 
I+π2s2I=estssin(πt)πests2cos(πt) 
I=estπ2+s2[s(sin(πt))+πcos(πt)] 
Step 3 
Now, we evaluate the Laplace transform of given function. 
L[f(t)]=[estπ2+s2[s(sin(πt))+πcos(πt)]]23 
 

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