# Help with f'(X)Watch

#1
Hey, I have been given a past exam paper and I cant remember how to/ what f'(x) means, can anyone explain it please?
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4 years ago
#2
(Original post by kaaatiiie)
Hey, I have been given a past exam paper and I cant remember how to/ what f'(x) means, can anyone explain it please?
Differentiate the function.
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#3
(Original post by rayquaza17)
Differentiate the function.
Thanks
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4 years ago
#4
(Original post by kaaatiiie)
Hey, I have been given a past exam paper and I cant remember how to/ what f'(x) means, can anyone explain it please?
It means that you should create the first derivation of a function by differentiating the term to determine the extreme values.
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#5
(Original post by Kallisto)
It means that you should create the first derivation of a function by differentiating the term to determine the extreme values.
Okay, Thanks

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4 years ago
#6
(Original post by kaaatiiie)
Okay, Thanks

You are welcome! the number of the 'apostrophes' above the function is the number of differentiations/derivations.
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4 years ago
#7
(Original post by Kallisto)
It means that you should create the first derivation of a function by differentiating the term to determine the extreme values.
No, f'(x) simply means differentiate f(x) with respect to x.

The bit in bold is just one possible application of differentiation, but it's not implied by the notation!
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4 years ago
#8
(Original post by Kallisto)
You are welcome! the number of the 'apostrophes' above the function is the number of differentiations/derivations.
I always assumed they were Roman numerals? That would make more sense for higher derivatives, I think.

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4 years ago
#9
(Original post by Manitude)
I always assumed they were Roman numerals? That would make more sense for higher derivatives, I think.

Posted from TSR Mobile
No I think they're just dashes.
After f'' people often just write etc. But like make sure the number is in brackets so you don't confuse it with taking powers of f!
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4 years ago
#10
(Original post by davros)
No, f'(x) simply means differentiate f(x) with respect to x.

The bit in bold is just one possible application of differentiation, but it's not implied by the notation!
Fair enough. I just wanted to explain the sense in analysis, sorry if I was not clear enough or too far in my explanation. Of course a function can be differentiated without a purpose.

(Original post by Manitude)
I always assumed they were Roman numerals? That would make more sense for higher derivatives, I think.
Yes, its right that Roman numerals are used in higher derivatives. But I have learnt to use the 'apostrophes' by the first three derivations. As I did not more than this number of derivations in analysis, I have never used Roman numerals.
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4 years ago
#11
(Original post by Kallisto)
Yes, its right that Roman numerals are used in higher derivatives. But I have learnt to use the 'apostrophes' by the first three derivations. As I did not more than this number of derivations in analysis, I have never used Roman numerals.
This seems interesting:

http://en.wikipedia.org/wiki/Notatio...e.27s_notation

I've never heard of using Roman numerals before now!
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4 years ago
#12
(Original post by rayquaza17)
This seems interesting:

http://en.wikipedia.org/wiki/Notatio...e.27s_notation

I've never heard of using Roman numerals before now!
Its interesting indeed, I don't know that there are so many different spellings for differentiations. I am used to write in Lagrange.
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4 years ago
#13
(Original post by Kallisto)
Yes, its right that Roman numerals are used in higher derivatives. But I have learnt to use the 'apostrophes' by the first three derivations. As I did not more than this number of derivations in analysis, I have never used Roman numerals.
Fair enough, I always refer to them as dashes anyway and also haven't used more than three derivations when writing functions like this. I'd personally be tempted to swap to df/dx notation for higher order derivatives though I imagine some people might take issue with that lack of consistency but I am not a mathematician so I can butcher notation with a clear conscience
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4 years ago
#14
(Original post by rayquaza17)
This seems interesting:

http://en.wikipedia.org/wiki/Notatio...e.27s_notation

I've never heard of using Roman numerals before now!
Interesting - I've used all of those except Euler's notation before. I also didn't realise these notations even had names! Newton's notation is used quite a lot in physics and the section on vector calculus brought back bitter-sweet memories of second year mathematics and third year fluid physics.
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