C4 Last Minute Question Thread (Today's the day - good luck!) Watch

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RDKGames
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Hello everybody :wavey:

Just as we had Last Minute threads last year, we are bringing them back for this year round too!

You can use this thread for any Core 4 revision you may be doing and may need a hand with, whatever your question! Please post it here and someone will be able to help you out
It doesn't matter whether you're on AQA, Edexcel, MEI, or whatever the exam board. This thread is all-inclusive.

When posting a question, make sure you post your attempt so that helpers know where you're stuck and can help you faster.

If you're looking for some C3 revision help, we also have a similar style thread here!

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Wazm_
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how do I integrate -sin2xsinx dx between pi/2 and 0
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RDKGames
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(Original post by Wazm_)
how do I integrate -sin2xsinx dx between pi/2 and 0
At first it's not obvious what to do but that \sin 2x is practically begging to be expressed differently.

So replace \sin 2x \equiv 2\sin x \cos x.

Then the leftover integrand of -2\sin^2x \cos x can be integrated by an obvious substitution, or even by inspection.
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Wazm_
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(Original post by RDKGames)
At first it's not obvious what to do but that \sin 2x is practically begging to be expressed differently.

So replace \sin 2x \equiv 2\sin x \cos x.

Then the leftover integrand of -2\sin^2x \cos x can be integrated by an obvious substitution, or even by inspection.
Thank you

I kept turning it to -2(intergal)cosx-cos^3x then kept trying to do parts and stuff and it wouldn work as it kept repeating
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ExiterGently
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Edexcel, integration, chapter 6, mixed exercise, page 125, Q30, part b.

hi I'm stuck on this question, I've had a look at the PMT solution bank and its confused me even more. Any help is greatly appreciated.
please and thank you xxxx


(I've tried uploading a picture of the q but its not letting me)
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Notnek
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(Original post by ExiterGently)
Edexcel, integration, chapter 6, mixed exercise, page 125, Q30, part b.

hi I'm stuck on this question, I've had a look at the PMT solution bank and its confused me even more. Any help is greatly appreciated.
please and thank you xxxx


(I've tried uploading a picture of the q but its not letting me)


Please post what you've tried and show us where you're stuck.
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ExiterGently
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(Original post by Notnek)


Please post what you've tried and show us where you're stuck.
for some reason its not letting me upload pictures of my working. But put into words I've tried to integrate by parts using the uv formula and im stuck
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Notnek
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(Original post by ExiterGently)
for some reason its not letting me upload pictures of my working. But put into words I've tried to integrate by parts using the uv formula and im stuck
You really need to show/explain more what you've done. If you upload via Imgur using this method. Alternatively please post your working in text form.
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Gasman17
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(Original post by ExiterGently)
Edexcel, integration, chapter 6, mixed exercise, page 125, Q30, part b.

hi I'm stuck on this question, I've had a look at the PMT solution bank and its confused me even more. Any help is greatly appreciated.
please and thank you xxxx


(I've tried uploading a picture of the q but its not letting me)
Here Is my working hope it helps
https://drive.google.com/file/d/1L29...w?usp=drivesdk
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ExiterGently
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(Original post by Notnek)
You really need to show/explain more what you've done. If you upload via Imgur using this method. Alternatively please post your working in text form.


https://imgur.com/a/CQvkfSO
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LkCtl
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(Original post by ExiterGently)
for some reason its not letting me upload pictures of my working. But put into words I've tried to integrate by parts using the uv formula and im stuck
Do you know how you're supposed to begin a differential equations question? Bring dx up to the right hand side and then separate out your x and y terms so that all of your x's are on the same side as dx and all of your y terms are on the same side as dy. Without any of your working it's hard to say, but it sounds like you've just tried to integrate dy/dx as it's given. You can't try to integrate an equation with x's and y's.

Instead because you have an equation in x multiplied by dx and an equation in y multiplied by dy, you can imagine there's an integral sign in front of both and integrate them separately to get two equal results. You should notice that your 'dx' side is the same as what you integrated in part (a), so you just need to integrate the trig function in y.

As a rule, if you want to integrate a squared trig function, you should look at the double angle formula for cosine. In this case: cos2x = 2cos^2x - 1. You can rearrange this for an easier to integrate function.

Any question which calls itself a 'differential equation' will follow this general pattern of separating out your variables, as there's no 'implicit integration'.
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Notnek
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(Original post by ExiterGently)
X
I'm a bit confused what you've done here. Have you separated the variables? You need the y's on one side and the x's on the other. It doesn't look like you've done that.
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username3694440
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Is there a general approach or 'fixed' method for the binomial questions where they ask you to evaluate e.g root 360 (an example is question 2c on this paper http://pmt.physicsandmathstutor.com/...%20Edexcel.pdf). Normally when I'm doing these questions I don't really know what I'm doing so I just sort of fiddle around with it until it gets the right answer. What's the proper way of doing these types of questions? Thank you!
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MR1999
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Plug your value of x into the binomial and rewrite it as the number you're trying to approximate.

 (4-0.01)^{\frac{1}{2}}=\sqrt{3.99}=  \sqrt{\dfrac{399}{100}}=\dfrac{1  }{10}\sqrt{399}

You can now plug your value of x in and then rearrange.

Hello2903
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Notnek
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(Original post by MR1999)
Plug your value of x into the binomial and rewrite it as the number you're trying to approximate.

 (4-0.01)^{\frac{1}{2}}=\sqrt{3.99}=  \sqrt{\efrac{399}{100}}=\dfrac{1  }{10}\sqrt{399}

You can now plug your value of x in and then rearrange.
I think you quoted the wrong person.
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MR1999
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(Original post by Notnek)
I think you quoted the wrong person.
Thanks.
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ExiterGently
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(Original post by Lukesj)
Do you know how you're supposed to begin a differential equations question? Bring dx up to the right hand side and then separate out your x and y terms so that all of your x's are on the same side as dx and all of your y terms are on the same side as dy. Without any of your working it's hard to say, but it sounds like you've just tried to integrate dy/dx as it's given. You can't try to integrate an equation with x's and y's.

Instead because you have an equation in x multiplied by dx and an equation in y multiplied by dy, you can imagine there's an integral sign in front of both and integrate them separately to get two equal results. You should notice that your 'dx' side is the same as what you integrated in part (a), so you just need to integrate the trig function in y.

As a rule, if you want to integrate a squared trig function, you should look at the double angle formula for cosine. In this case: cos2x = 2cos^2x - 1. You can rearrange this for an easier to integrate function.

Any question which calls itself a 'differential equation' will follow this general pattern of separating out your variables, as there's no 'implicit integration'.
tysm <333333
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ExiterGently
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edexcel c4, practice paper, page 140, question5

hi I'm stuck on this question can someone clear a path for me, please and thank you xx


(still not allowed to upload & imgur is down so i used tumblr hope thats ok)

https://www.tumblr.com/blog/exitergently
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ExiterGently
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dexcel c4, practice paper, page 140, question5

hi I'm stuck on this question can someone clear a path for me, please and thank you xx


(still not allowed to upload & imgur is down so i used tumblr hope thats ok)

https://www.tumblr.com/blog/exitergently
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Notnek
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(Original post by ExiterGently)
dexcel c4, practice paper, page 140, question5

hi I'm stuck on this question can someone clear a path for me, please and thank you xx


(still not allowed to upload & imgur is down so i used tumblr hope thats ok)

https://www.tumblr.com/blog/exitergently
Hi, I’m unable to view that link. - I don’t know if others can. Please try a free image uoloader website.
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