The Student Room Group

Help with taylor expansion.

Around x-=0 to x^2

(sin(x)/x)^1/2

I get quite far but cant simplify it.. just the final step.
Reply 1
Original post by shahbaz
Around x-=0 to x^2

(sin(x)/x)^1/2

I get quite far but cant simplify it.. just the final step.


please post what you have done so far
(my method is through standard expansions and binomial)
Reply 2
Original post by TeeEm
please post what you have done so far
(my method is through standard expansions and binomial)


Firstly I used the expansion sinx = x-(x^3)/3!)+.....
then I divided by x to give 1-(x^2)/3!
Then I square rooted it thats as far as i can get
I know the method is correct but the final solution was 1-x^2/12
Reply 3
Original post by shahbaz
Firstly I used the expansion sinx = x-(x^3)/3!)+.....
then I divided by x to give 1-(x^2)/3!

Then I square rooted it thats as far as i can get
I know the method is correct but the final solution was 1-x^2/12



I agree with the blue

I do not quite understand the red bit ...
Original post by shahbaz
Firstly I used the expansion sinx = x-(x^3)/3!)+.....
then I divided by x to give 1-(x^2)/3!
Then I square rooted it thats as far as i can get
I know the method is correct but the final solution was 1-x^2/12
Binomial theorem:

(1-A)^(1/2) = 1 - A/2 + O(A^2).

Apply with A= x^2/3!
Reply 5
Original post by TeeEm
I agree with the blue

I do not quite understand the red bit ...


You have to square root the entire thing to get it into the form the question wants.
Reply 6
Original post by DFranklin
Binomial theorem:

(1-A)^(1/2) = 1 - A/2 + O(A^2).

Apply with A= x^2/3!


Thanks will try it now.
Reply 7
Original post by shahbaz
You have to square root the entire thing to get it into the form the question wants.


I hope you do not mean what I suspect you mean

After that it is just the first 2 terms of a binomial expansion to 1/2
Reply 8
Original post by DFranklin
Binomial theorem:

(1-A)^(1/2) = 1 - A/2 + O(A^2).

Apply with A= x^2/3!


it worked! I'm pretty bad at spotting things like that. Thanks again.
Reply 9
Original post by TeeEm
I hope you do not mean what I suspect you mean

After that it is just the first 2 terms of a binomial expansion to 1/2


Yeah, I know now, be kind its only my first year lol.
Reply 10
Original post by shahbaz
Yeah, I know now, be kind its only my first year lol.


no worries

(+5 reciprocated)
(edited 9 years ago)

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