Laplace Transform of $f(t) = u(sin(2t))$?

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What is the Laplace Transform of $f(t) = u(sin(2t))$?



I'm confused how to proceed further? because $u(t)=0$ for t<0. What does having $sin(2t)$ in argument mean?



Or $u$ has to be taken as unknown function?







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  • 2




    Welcome to MSE. It will be more likely that you will get an answer if you show us that you made an effort. This should be added to the question rather than in the comments.
    – José Carlos Santos
    Jul 30 at 7:32






  • 1




    I've always seen $u$ defined as $1$ for $t>0$, and $0$ for $t<0$. But this (or another) definition should be given to you, not guessed at.
    – mr_e_man
    Jul 30 at 7:34














up vote
-2
down vote

favorite












What is the Laplace Transform of $f(t) = u(sin(2t))$?



I'm confused how to proceed further? because $u(t)=0$ for t<0. What does having $sin(2t)$ in argument mean?



Or $u$ has to be taken as unknown function?







share|cite|improve this question

















  • 2




    Welcome to MSE. It will be more likely that you will get an answer if you show us that you made an effort. This should be added to the question rather than in the comments.
    – José Carlos Santos
    Jul 30 at 7:32






  • 1




    I've always seen $u$ defined as $1$ for $t>0$, and $0$ for $t<0$. But this (or another) definition should be given to you, not guessed at.
    – mr_e_man
    Jul 30 at 7:34












up vote
-2
down vote

favorite









up vote
-2
down vote

favorite











What is the Laplace Transform of $f(t) = u(sin(2t))$?



I'm confused how to proceed further? because $u(t)=0$ for t<0. What does having $sin(2t)$ in argument mean?



Or $u$ has to be taken as unknown function?







share|cite|improve this question













What is the Laplace Transform of $f(t) = u(sin(2t))$?



I'm confused how to proceed further? because $u(t)=0$ for t<0. What does having $sin(2t)$ in argument mean?



Or $u$ has to be taken as unknown function?









share|cite|improve this question












share|cite|improve this question




share|cite|improve this question








edited Jul 30 at 8:44
























asked Jul 30 at 7:25









Akash Kishore

33




33







  • 2




    Welcome to MSE. It will be more likely that you will get an answer if you show us that you made an effort. This should be added to the question rather than in the comments.
    – José Carlos Santos
    Jul 30 at 7:32






  • 1




    I've always seen $u$ defined as $1$ for $t>0$, and $0$ for $t<0$. But this (or another) definition should be given to you, not guessed at.
    – mr_e_man
    Jul 30 at 7:34












  • 2




    Welcome to MSE. It will be more likely that you will get an answer if you show us that you made an effort. This should be added to the question rather than in the comments.
    – José Carlos Santos
    Jul 30 at 7:32






  • 1




    I've always seen $u$ defined as $1$ for $t>0$, and $0$ for $t<0$. But this (or another) definition should be given to you, not guessed at.
    – mr_e_man
    Jul 30 at 7:34







2




2




Welcome to MSE. It will be more likely that you will get an answer if you show us that you made an effort. This should be added to the question rather than in the comments.
– José Carlos Santos
Jul 30 at 7:32




Welcome to MSE. It will be more likely that you will get an answer if you show us that you made an effort. This should be added to the question rather than in the comments.
– José Carlos Santos
Jul 30 at 7:32




1




1




I've always seen $u$ defined as $1$ for $t>0$, and $0$ for $t<0$. But this (or another) definition should be given to you, not guessed at.
– mr_e_man
Jul 30 at 7:34




I've always seen $u$ defined as $1$ for $t>0$, and $0$ for $t<0$. But this (or another) definition should be given to you, not guessed at.
– mr_e_man
Jul 30 at 7:34










1 Answer
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If $u(t) = 1$ for positive $t$, and $0$ otherwise, then $u(sin(2t)) = 1$ whenever $sin(2t)$ is positive.



That is, $f(t) = 1$ whenever $2t$ is in one of the intervals $(0,pi),;(2pi,3pi),;(4pi,5pi),;(-2pi,-pi),;cdots$



meaning $t$ is in one of the intervals $(0,fracpi2),;(pi,frac3pi2),;(2pi,frac5pi2),;(-pi,-fracpi2),;cdots$



and $f(t) = 0$ otherwise. This is a square wave.






share|cite|improve this answer





















  • Yes i wrote the defn of step function wrongly. And Thanks for Solution
    – Akash Kishore
    Jul 30 at 8:44










  • The Laplace transform of $f$ is not a square wave; I just set up the problem for you to finish. Or did you already? If so, click on the check mark to "accept" this answer.
    – mr_e_man
    Jul 30 at 8:46










  • Yes i understood that f(t) is a square wave
    – Akash Kishore
    Jul 30 at 8:50











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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
1
down vote



accepted










If $u(t) = 1$ for positive $t$, and $0$ otherwise, then $u(sin(2t)) = 1$ whenever $sin(2t)$ is positive.



That is, $f(t) = 1$ whenever $2t$ is in one of the intervals $(0,pi),;(2pi,3pi),;(4pi,5pi),;(-2pi,-pi),;cdots$



meaning $t$ is in one of the intervals $(0,fracpi2),;(pi,frac3pi2),;(2pi,frac5pi2),;(-pi,-fracpi2),;cdots$



and $f(t) = 0$ otherwise. This is a square wave.






share|cite|improve this answer





















  • Yes i wrote the defn of step function wrongly. And Thanks for Solution
    – Akash Kishore
    Jul 30 at 8:44










  • The Laplace transform of $f$ is not a square wave; I just set up the problem for you to finish. Or did you already? If so, click on the check mark to "accept" this answer.
    – mr_e_man
    Jul 30 at 8:46










  • Yes i understood that f(t) is a square wave
    – Akash Kishore
    Jul 30 at 8:50















up vote
1
down vote



accepted










If $u(t) = 1$ for positive $t$, and $0$ otherwise, then $u(sin(2t)) = 1$ whenever $sin(2t)$ is positive.



That is, $f(t) = 1$ whenever $2t$ is in one of the intervals $(0,pi),;(2pi,3pi),;(4pi,5pi),;(-2pi,-pi),;cdots$



meaning $t$ is in one of the intervals $(0,fracpi2),;(pi,frac3pi2),;(2pi,frac5pi2),;(-pi,-fracpi2),;cdots$



and $f(t) = 0$ otherwise. This is a square wave.






share|cite|improve this answer





















  • Yes i wrote the defn of step function wrongly. And Thanks for Solution
    – Akash Kishore
    Jul 30 at 8:44










  • The Laplace transform of $f$ is not a square wave; I just set up the problem for you to finish. Or did you already? If so, click on the check mark to "accept" this answer.
    – mr_e_man
    Jul 30 at 8:46










  • Yes i understood that f(t) is a square wave
    – Akash Kishore
    Jul 30 at 8:50













up vote
1
down vote



accepted







up vote
1
down vote



accepted






If $u(t) = 1$ for positive $t$, and $0$ otherwise, then $u(sin(2t)) = 1$ whenever $sin(2t)$ is positive.



That is, $f(t) = 1$ whenever $2t$ is in one of the intervals $(0,pi),;(2pi,3pi),;(4pi,5pi),;(-2pi,-pi),;cdots$



meaning $t$ is in one of the intervals $(0,fracpi2),;(pi,frac3pi2),;(2pi,frac5pi2),;(-pi,-fracpi2),;cdots$



and $f(t) = 0$ otherwise. This is a square wave.






share|cite|improve this answer













If $u(t) = 1$ for positive $t$, and $0$ otherwise, then $u(sin(2t)) = 1$ whenever $sin(2t)$ is positive.



That is, $f(t) = 1$ whenever $2t$ is in one of the intervals $(0,pi),;(2pi,3pi),;(4pi,5pi),;(-2pi,-pi),;cdots$



meaning $t$ is in one of the intervals $(0,fracpi2),;(pi,frac3pi2),;(2pi,frac5pi2),;(-pi,-fracpi2),;cdots$



and $f(t) = 0$ otherwise. This is a square wave.







share|cite|improve this answer













share|cite|improve this answer



share|cite|improve this answer











answered Jul 30 at 7:46









mr_e_man

748219




748219











  • Yes i wrote the defn of step function wrongly. And Thanks for Solution
    – Akash Kishore
    Jul 30 at 8:44










  • The Laplace transform of $f$ is not a square wave; I just set up the problem for you to finish. Or did you already? If so, click on the check mark to "accept" this answer.
    – mr_e_man
    Jul 30 at 8:46










  • Yes i understood that f(t) is a square wave
    – Akash Kishore
    Jul 30 at 8:50

















  • Yes i wrote the defn of step function wrongly. And Thanks for Solution
    – Akash Kishore
    Jul 30 at 8:44










  • The Laplace transform of $f$ is not a square wave; I just set up the problem for you to finish. Or did you already? If so, click on the check mark to "accept" this answer.
    – mr_e_man
    Jul 30 at 8:46










  • Yes i understood that f(t) is a square wave
    – Akash Kishore
    Jul 30 at 8:50
















Yes i wrote the defn of step function wrongly. And Thanks for Solution
– Akash Kishore
Jul 30 at 8:44




Yes i wrote the defn of step function wrongly. And Thanks for Solution
– Akash Kishore
Jul 30 at 8:44












The Laplace transform of $f$ is not a square wave; I just set up the problem for you to finish. Or did you already? If so, click on the check mark to "accept" this answer.
– mr_e_man
Jul 30 at 8:46




The Laplace transform of $f$ is not a square wave; I just set up the problem for you to finish. Or did you already? If so, click on the check mark to "accept" this answer.
– mr_e_man
Jul 30 at 8:46












Yes i understood that f(t) is a square wave
– Akash Kishore
Jul 30 at 8:50





Yes i understood that f(t) is a square wave
– Akash Kishore
Jul 30 at 8:50













 

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