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Reduction formula

How do you know what to let u and v equal when you have:

or sin^nx

In the edexcel book on page 75 it gives an example with sin^nx and used u=sin^n-1x and I don't understand why/how exactly
Reply 1
Avatar for TeeEm
TeeEm
19
Original post by Sapphiresmith
How do you know what to let u and v equal when you have:

or sin^nx

In the edexcel book on page 75 it gives an example with sin^nx and used u=sin^n-1x and I don't understand why/how exactly


you usually use integration by parts.

with experience you can see what you need to do.

if you cannot try it the way you thin it works and if it does not work try it the other way round
Original post by TeeEm
you usually use integration by parts.

with experience you can see what you need to do.

if you cannot try it the way you thin it works and if it does not work try it the other way round


The thing is I can find the reduction formula when I have x e or ln but when there are trig functions I don't understand what to do. I've been looking at the example in the book and I think it is quite confusing, so if you could please explain it step by step how to find the reduction formula when you have a trig function that would be useful (in particular with sin and cos)
Reply 3
Avatar for TeeEm
TeeEm
19
Original post by Sapphiresmith
The thing is I can find the reduction formula when I have x e or ln but when there are trig functions I don't understand what to do. I've been looking at the example in the book and I think it is quite confusing, so if you could please explain it step by step how to find the reduction formula when you have a trig function that would be useful (in particular with sin and cos)


difficult to explain as it very long ..,

see if this link with full solutions helps

http://madasmaths.com/archive/maths_booklets/further_topics/integration/reduction_formulas.pdf
Original post by TeeEm
difficult to explain as it very long ..,

see if this link with full solutions helps

http://madasmaths.com/archive/maths_booklets/further_topics/integration/reduction_formulas.pdf


Thanks for the link but everytime I click on the proofs nothing happens. Is there a way to make it larger so I can view it better?
Reply 5
Avatar for TeeEm
TeeEm
19
Original post by Sapphiresmith
Thanks for the link but everytime I click on the proofs nothing happens. Is there a way to make it larger so I can view it better?


it is a PDF file not a web file like a pop up.

download it and enlarge it on your computer NOT on the webpage
Original post by Sapphiresmith
How do you know what to let u and v equal when you have:

or sin^nx

In the edexcel book on page 75 it gives an example with sin^nx and used u=sin^n-1x and I don't understand why/how exactly



Heya, is this still causing you grief?
Original post by BanoffeeGuy
Heya, is this still causing you grief?


Please don't bump old threads for no good reason.
Original post by Mr M
Please don't bump old threads for no good reason.


I'll be honest, I can't understand why.
Original post by BanoffeeGuy
I'll be honest, I can't understand why.


I was just making you aware of one of the Study Help Rules.

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