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# Ln |x| or Ln (x) or Ln x Tweet

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1. Ln |x| or Ln (x) or Ln x
Does it matter whether you write (e.g.) ln|sec x| or ln(sec x) in the Edexcel C4 exam... (as in do you use brackets or straight lines?)
2. Re: Ln |x| or Ln (x) or Ln x
Bump
3. Re: Ln |x| or Ln (x) or Ln x
Modulus is different to brackets, as in

Might be wrong but that's my understanding of the C modules
Last edited by SubAtomic; 19-06-2012 at 23:26.
4. Re: Ln |x| or Ln (x) or Ln x
(Original post by SubAtomic)
Modulus is different to brackets, as in
It is but I don't think it's necessary to use the modulus in ln in A-level maths. They seem to just ignore the fact there's a modulus there most of the time in the integration/differentiation chaptes.
5. Re: Ln |x| or Ln (x) or Ln x
(Original post by hassi94)
It is but I don't think it's necessary to use the modulus in ln in A-level maths. They seem to just ignore the fact there's a modulus there most of the time in the integration/differentiation chaptes.
ln(sec x) wouldn't work though would it if sec x returned negative value? Cannot say have ever done anything/much with secant so no idea yet.
Last edited by SubAtomic; 19-06-2012 at 23:33.
6. Re: Ln |x| or Ln (x) or Ln x
If you have a definite integral and you get your answer in temrs of Ln with limits of somehting like 3 and 4 and end up with Ln (X-6) + ln(x-5), once you plug it in, you're supposed to take the modulus of the inside bracket so to avoid confusion I'd say keep your modulus.
7. Re: Ln |x| or Ln (x) or Ln x
If you don't put in the modulus, and no range of is specified by the question, then the answer is wrong! So you have to put the modulus signs. But if you don't then you will probably drop a mark, so nothing catastrophic.
8. Re: Ln |x| or Ln (x) or Ln x
(Original post by sabre2th1)
Does it matter whether you write (e.g.) ln|sec x| or ln(sec x) in the Edexcel C4 exam... (as in do you use brackets or straight lines?)
when integrating f'(x)/f(x) always goes to ln|f(x)| otherwise normal brackets are fine
9. Re: Ln |x| or Ln (x) or Ln x
(Original post by nuodai)
If you don't put in the modulus, and no range of is specified by the question, then the answer is wrong! So you have to put the modulus signs. But if you don't then you will probably drop a mark, so nothing catastrophic.
I think, for the A level course they just assume x>0.

I've seen mark schemes with no modulus signs mentioned.
10. Re: Ln |x| or Ln (x) or Ln x
Mathematically, it should be modulus unless it's implied in the question (I.E. x>0 is stated). But I've never seen a markscheme that cared.
11. Re: Ln |x| or Ln (x) or Ln x
I think, for the A level course they just assume x>0.

I've seen mark schemes with no modulus signs mentioned.
That doesn't make it right! And you certainly won't be marked down for using modulus signs. It seems silly to leave them out and risk losing marks.
12. Re: Ln |x| or Ln (x) or Ln x
(Original post by nuodai)
That doesn't make it right! And you certainly won't be marked down for using modulus signs. It seems silly to leave them out and risk losing marks.
I never said it was correct to remove the modulus signs, my point is that they (the examiner) doesn't really care about them.
13. Re: Ln |x| or Ln (x) or Ln x
The book generally uses the modulus and so does our formula book...I was taught to use it, so I presume it is needed, if anything just to make equations mathematically correct more than to not drop a mark.

I doubt you would lose a mark if not including it.