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Guessing the particular integral. PLEASE HELP

For an assignment on my maths uni course, I have been asked in each case below, to give the particular integral which you should try, in a format that includes unknown constants. I am not required to do any working or substitution, just give the particular integral guess. Any help would be greatly appreciated.

a) h(t)=sin3t
b) h(t)=e^t
c) h(t)=e^t (sin6t)
d) h(t)=e^4t (sin3t)
e) h(t)=e^t (sin3t)
f) h(t)=5e^t (cos3t)
Original post by Lollieboo
For an assignment on my maths uni course, I have been asked in each case below, to give the particular integral which you should try, in a format that includes unknown constants. I am not required to do any working or substitution, just give the particular integral guess. Any help would be greatly appreciated.

a) h(t)=sin3t
b) h(t)=e^t
c) h(t)=e^t (sin6t)
d) h(t)=e^4t (sin3t)
e) h(t)=e^t (sin3t)
f) h(t)=5e^t (cos3t)


What do you think? Don't you have any notes on this?

For example, the first one would be Acos(3t)+Bsin(3t)A\cos(3t) + B \sin(3t).
Reply 2
Original post by RDKGames
What do you think? Don't you have any notes on this?

For example, the first one would be Acos(3t)+Bsin(3t)A\cos(3t) + B \sin(3t).


I have a few notes. for example, I think that as you say, the first would be x=Csin3t + Dcos2t, and for part b) I think it would be x = Ce^t. However, I haven't been given any notes on what to do when you have an exponential and a trigonometric part combined.
Original post by Lollieboo
I have a few notes. for example, I think that as you say, the first would be x=Csin3t + Dcos2t, and for part b) I think it would be x = Ce^t. However, I haven't been given any notes on what to do when you have an exponential and a trigonometric part combined.


Have an educated guess. Hint: it's a combination of both P.I's.
Reply 4
Original post by RDKGames
Have an educated guess. Hint: it's a combination of both P.I's.


Would d) be x = Ae4t(sin3t) + Be4t(cos3t) ???
Original post by Lollieboo
Would d) be x = Ae4t(sin3t) + Be4t(cos3t) ???


Yep, so you can leave it as e4t(Asin3t+Bcos3t)e^{4t}(A\sin 3t + B\cos 3t) for simplicity.
Reply 6
Original post by RDKGames
Yep, so you can leave it as e4t(Asin3t+Bcos3t)e^{4t}(A\sin 3t + B\cos 3t) for simplicity.


Fantastic. Does it change at all for f) given the 5 before the function? I'm assuming it doesn't affect the particular integral.
Original post by Lollieboo
Fantastic. Does it change at all for f) given the 5 before the function? I'm assuming it doesn't affect the particular integral.


That doesn't matter.
Reply 8
Original post by RDKGames
That doesn't matter.


Thanks for the help

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