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# How to integrate cos^2 (4x)-c4 Watch

1. How to integrate cos^2 (4x) using double angle formula
2. (Original post by James Cameron)
How to integrate cos^2 (4x) using double angle formula
As you have said ... Use double angle formula

Cos8x =
3. (Original post by TenOfThem)
As you have said ... Use double angle formula

Cos8x =
i'm uncertain as to the steps required when there's a coefficient to the x
4. (Original post by TenOfThem)
As you have said ... Use double angle formula

Cos8x =
Lol
5. (Original post by James Cameron)
i'm uncertain as to the steps required when there's a coefficient to the x
The same steps as with x on its own.
6. (Original post by zetamcfc)
The same steps as with x on its own.
7. (Original post by James Cameron)
How to integrate cos^2 (4x) using double angle formula
Cos8x = 2cos^2(4x) - 1
So cos^2(4x) = (1/2)cos8x + (1/2)
Integrate that and you get (1/16)sin8x + (1/2)x + c

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8. (Original post by James Cameron)
Can you do the question for cos^2x by using cos2x

If so .... This question is the same using cos8x
9. (Original post by powelsmartin)
Cos8x = 2cos^2(4x) - 1
So cos^2(4x) = (1/2)cos8x + (1/2)
Integrate that and you get (1/16)sin8x + (1/2)x + c

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Please do not post full solutions
10. (Original post by TenOfThem)
Please do not post full solutions
Apologies, I'm new to the forum - don't know all the rules yet!

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11. (Original post by James Cameron)
12. (Original post by powelsmartin)
Apologies, I'm new to the forum - don't know all the rules yet!

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No problem .... The guidelines ask us to guide and prompt ... Giving solutions only as a last resort
13. (Original post by powelsmartin)
Cos8x = 2cos^2(4x) - 1
So cos^2(4x) = (1/2)cos8x + (1/2)
Integrate that and you get (1/16)sin8x + (1/2)x + c

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Thank you so much, could you also help me find the integral of

sin4xcos3x
14. (Original post by James Cameron)
It is better for you to write your solution then others will check it, rather than give you the answers...
15. (Original post by zetamcfc)
It is better for you to write your solution then others will check it, rather than give you the answers...
OK i'll attempt to solve it now, thanks
16. (Original post by James Cameron)
Thank you so much, could you also help me find the integral of

sin4xcos3x

You should see a very useful formula for rewriting sinAcosB in terms of other things
17. (Original post by James Cameron)
Thank you so much, could you also help me find the integral of

sin4xcos3x
Do you own a formula book? The formula to use is in there (For AQA at least).
18. (Original post by zetamcfc)
Do you own a formula book? The formula to use is in there (For AQA at least).
WHich formula would help here?
19. (Original post by James Cameron)
WHich formula would help here?
AS davros said, in a previous post...
20. (Original post by zetamcfc)
AS davros said, in a previous post...
Well i don't have a formula book on me right now, would the formula you're talking about be sin(a+b)=sinacosb+sinbcosa

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