Differential notation

  • Thread starter nokia8650
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  • #1
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If one was to differntiate a function implicity eg.

sin x + cos y = 5,

would one show this by writing:

d/dx(sin x + cos y = 5)

= and then differentiate with respect to x? I wasnt sure whether or not the bracket goes around the whole thing or just the left hand side.


Thanks
 

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  • #2
tiny-tim
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If one was to differntiate a function implicity eg.

sin x + cos y = 5,

would one show this by writing:

d/dx(sin x + cos y = 5)

= and then differentiate with respect to x? I wasnt sure whether or not the bracket goes around the whole thing or just the left hand side.


Thanks
Hi nokia8650! :smile:

Definitely the whole thing!

Whatever you do to one side of an equation, you must do to the other.

:smile: That's what equality is all about! :smile:
 
  • #3
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Hmm, I never thought about that. Now I'll know it's correct
However, I use this notation
[tex]\sin{x}+\cos{y}=5\mid\cdot{d/dx}[/tex]
it's just seems more convenient
That's exactly the same thing isn't it?

I know it's a REALLY silly question but I just wanted to make sure
 
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  • #4
tiny-tim
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[tex]\sin{x}+\cos{y}=5\mid\cdot{d/dx}[/tex]
Hi armis! :smile:

(are you the same person as nokia8650?)

I don't really understand that.

Can you show how the next couple of lines would go, so that we can see it in actual use? :smile:
 
  • #5
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Hi tiny-tim

Nop, I am not the same person :)

Sure
[tex]\sin{x}+\cos{y}=5\mid\cdot{d/dx}[/tex]
We get
[tex]\cos{x}=0[/tex] if y is not a function of x

Most of our lecturers do that so I was wondering why bother writting ()
 
  • #6
tiny-tim
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Hi armis! :smile:

It looks weird to me …

but if your lecturers do it, I suppose it's ok.

I think writing the () is better because it avoids any possibility of ambiguity …

also, that vertical stroke may be clear on a whiteboard, where the lecturer can make it really large, but it's not so clear on paper or in a book. :frown:
 
  • #7
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I find it wierd you haven't seen it :) Well, maby I am the wierd one and it may just be a matter of convenience for the lecturers as sometimes they have to write down REALLY a lot of stuff on the whiteboard
I am just so used to it that I could hardly think of writting () :)
But yeah, () avoids any possibility of ambiguity (phew.... that was a hard one for me, I am not an english speaker)
Indeed the vertical stroke is larger than the one I showed as I couldn't find one large enough in the LaTeX
 

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