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C4 integration Q

Trying to integrate y = e^(2x) sin(2x)

I've tried integration by parts, but this seems to take me round in circles. Is it maybe substituion?
Original post by adam132
Trying to integrate y = e^(2x) sin(2x)

I've tried integration by parts, but this seems to take me round in circles. Is it maybe substituion?


No, it is parts

You should get

I = function + (fraction)I

And then be able to rearrange
Original post by TenOfThem
No, it is parts

You should get

I = function + (fraction)I

And then be able to rearrange


sorry, d'you think you could explain?

this is me attempting parts:

u = sin(2x) v = 1/2 e^(2x)
du/dx = 2cos(2x) dv/dx = e^(2x)


so:
uv - I(v*du/dx)
0.5sin(2x)e^(2x) - I(e^(2x)cos(2x))
doing by parts on the red part then takes me round to integrating e^(2x)sin(2x) (the original equation)

apologies if not very readable
Original post by adam132
sorry, d'you think you could explain?

this is me attempting parts:

u = sin(2x) v = 1/2 e^(2x)
du/dx = 2cos(2x) dv/dx = e^(2x)


so:
uv - I(v*du/dx)
0.5sin(2x)e^(2x) - I(e^(2x)cos(2x))
doing by parts on the red part then takes me round to integrating e^(2x)sin(2x) (the original equation)

apologies if not very readable

Exactly. When you get the original integral, you can call it I and rearrange.
ImageUploadedByStudent Room1398978704.765973.jpg

Okay so this is my working, what would I do at the end?

Edit: the last part shouldn't be 0.5

Posted from TSR Mobile
(edited 9 years ago)
Original post by adam132

Okay so this is my working, what would I do at the end?

Edit: the last part shouldn't be 0.5

Posted from TSR Mobile


You can now add I (the original integral) to both sides, getting 2I = ...

Then half it to get your answer.
Cheers guys, I understand it now. This seems pretty tricky though, would this sort of question come up?
Original post by adam132
Cheers guys, I understand it now. This seems pretty tricky though, would this sort of question come up?


I've never seen a question that hard, at least in the Edexcel specification I was on. However, there's nothing to say it won't come up. But you know the technique to solve it now.
Original post by PythianLegume
I've never seen a question that hard, at least in the Edexcel specification I was on. However, there's nothing to say it won't come up. But you know the technique to solve it now.


that's true I guess :smile:


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