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I don’t get why the 1/2 comes out of the integral
I got this but idk how
IMG_2557.jpegIMG_2558.jpeg
(edited 11 months ago)
Original post by Alevelhelp.1
I don’t get why the 1/2 comes out of the integral
I got this but idk how


cant see an attachment but you can take constants out of the integral as if you're taking it outside brackets
Reply 2
Original post by user8937264980
cant see an attachment but you can take constants out of the integral as if you're taking it outside brackets


Hey I just added it in
Original post by Alevelhelp.1
Hey I just added it in


taking the 1/2 outside the integral won't change the answer you get it just makes the working easier. if you have left the half inside the integral and got the wrong answer then your working has gone wrong somewhere
(edited 11 months ago)
Reply 4
Original post by user8937264980
taking the 1/2 outside the integral won't change the answer you get it just makes the working easier. if you have left the half inside the integral and got the wrong answer then your working has gone wrong somewhere


Is my working right then?
Original post by Alevelhelp.1
Is my working right then?


did you get the right answer if you expand the brackets to the power of 3/2. if you didnt get the right final answer then no. if you need help integrating it let me know
Reply 6
Original post by user8937264980
did you get the right answer if you expand the brackets to the power of 3/2. if you didnt get the right final answer then no. if you need help integrating it let me know

I got the wrong answer :frown: plz help
Original post by Alevelhelp.1
I got the wrong answer :frown: plz help


does the question ask you to use small angle approximation to integrate? can you attach it please?
Reply 8
Original post by user8937264980
does the question ask you to use small angle approximation to integrate? can you attach it please?

Cos theta equals 1-(theta)squared over 1
I’ve not got it rn but it’s just the cos theta one u can search it up
(edited 11 months ago)
Original post by Alevelhelp.1
Cos theta equals 1-(theta)squared over 1
I’ve not got it rn but it’s just the cos theta one u can search it up


no i mean does the question specify you have to use this or can you just integrate root cosx. and are you able to upload the actual question
(edited 11 months ago)
Reply 10
Original post by user8937264980
no i mean does the question specify you have to use this or can you just integrate root cosx. and are you able to upload the actual question


Yeah the q says use this, I’ve lost the question now sorry but can u help with what’s given plz 😭
(edited 11 months ago)
Reply 11
Original post by Alevelhelp.1
Yeah the q says use this, I’ve lost the question now sorry but can u help with what’s given plz 😭

Your working looks like complete nonsense tbh - try differentiating what you've written and see if gives you back the thing you're trying to integrate!

All they've done is apply a binomial approx to the square root in the integral and then integrate the resulting expression. I'm not actually sure why they took the 1/2 outside the integral just to put it back in again, but it doesn't change the answer!
Reply 12
Original post by davros
Your working looks like complete nonsense tbh - try differentiating what you've written and see if gives you back the thing you're trying to integrate!

All they've done is apply a binomial approx to the square root in the integral and then integrate the resulting expression. I'm not actually sure why they took the 1/2 outside the integral just to put it back in again, but it doesn't change the answer!


I used the chain rule but idk
Reply 13
Original post by Alevelhelp.1
I used the chain rule but idk


The chain rule is for differentiation, not integration. If you differentiate your answer, you should get back to the thing inside the integral (the "integrand"), whereas you will actually get back something horrible! they're actually trying to help you in this question by using a binomial approximation which is easy to integrate :smile:
Reply 14
Original post by davros
The chain rule is for differentiation, not integration. If you differentiate your answer, you should get back to the thing inside the integral (the "integrand"), whereas you will actually get back something horrible! they're actually trying to help you in this question by using a binomial approximation which is easy to integrate :smile:


I’m stuck… I don’t know what to do after this IMG_2565.jpeg
Reply 15
Original post by Alevelhelp.1
I’m stuck… I don’t know what to do after this IMG_2565.jpeg


it looks like they've just stuck in the binomial approx for (1 + r)^(1/2) where r = -x^2/2. You haven't posted the original question so I don't know if they suggested it or you're supposed to work it out, but it's part of the infinite series approx for that function (which would only converge for certain values, but they're only using 2 terms as an approximation).

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