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# C4 Integration help please Watch

1. Could someone help me with this question please:

How would i integrate ?
This is Question 1h Exercise 6C from C4 book.
................................ ................................ .....
2. Well you do need to use double angle formula but you can just reapply to deal with

3. (Original post by nm786)
Could someone help me with this question please:

How would i integrate ?
This is Question 1h Exercise 6C from C4 book.

This is what i did:
and
So, and
multiplying both of these:
what should i do next? I'm confused.
4. (Original post by nerak99)
Well you do need to use double angle formula but you can just reapply to deal with

Thanks for replying mate, so sould i sub this into the last equation and and integrate?: 1/2(1/2(cos4x+1)+1)
5. Well, working from what you did you could do that (I have not checked your working) but what Mr M showed you is a more elegant way of working if you want to take it from the top.
You need to use

Mr M has use and squared it.
6. (Original post by nerak99)
Well, working from what you did you could do that (I have not checked your working) but what Mr M showed you is a more elegant way of working if you want to take it from the top.
You need to use

Mr M has use and squared it.
so from what i did: 1/2(1/2(cos4x+1)+1)
=1/2(1/2cos4x+1/2+1)
=1/4cos4x+1/4+1/2
integrating above = 1/4*1/4sin4x+1/4x+1/2x+c
=1/16sin4x+3/4x+c

I'll use the equation Mr M suggested in a minute.
7. (Original post by Mr M)
I understand how you got that now but how would i go about integrating it?
8. (Original post by nm786)
I understand how you got that now but how would i go about integrating it?
You should know that
9. (Original post by Mr M)
You should know that
i never knew that
10. (Original post by nm786)
i never knew that
It is a key fact in Core 4 integration.

but that is not relevant to this question.
11. (Original post by Mr M)
It is a key fact in Core 4 integration.

but that is not relevant to this question.
alright i get it this is from cos2x identity right?
12. (Original post by nm786)
alright i get it this is from cos2x identity right?
how would i do this question sir,
using what you said:

using the identities and multiplying them together and 1/2:

I can use

integrating above i get i have no idea where i went wrong
You make things so complicated!

13. (Original post by Mr M)
You make things so complicated!

i don't understand how you went from
14. (Original post by nm786)
i don't understand how you went from
Post 9?
15. (Original post by Mr M)
Post 9?
oh yeah sorry,
so

Cheers Sir!
16. (Original post by nm786)
oh yeah sorry,
so

Cheers Sir!
17. (Original post by Mr M)
damn it i forgot the x
Much appreciated for the help sir!
18. (Original post by nm786)
damn it i forgot the x
Much appreciated for the help sir!
You are welcome.
19. (Original post by nm786)
alright i get it this is from cos2x identity right?
how would i do this question then sir,
using what you said:
do you think to

here
using the identities and multiplying them together and 1/2:
There would not be 'and 1/2'

That is without 1/2 factor

which is same that was said to you.
I can use again so
Just little difference only
Consider that
(and +1/4 at the end)

integrating above i get i have no idea where i went wrong the answer is something else
20. (Original post by ztibor)
do you think to

here

There would not be 'and 1/2'

That is without 1/2 factor

which is same that was said to you.

Just little difference only
Consider that
(and +1/4 at the end)

He finished the question 25 minutes ago.

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