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  Discussion about math, puzzles, games and fun.   Useful symbols: √ ∞ ≠ ≤ ≥ ≈ ⇒ ∈ Δ θ ∴ ∑ ∫ π -

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Topic review (newest first)

anonimnystefy
2012-10-27 10:29:54

That looks ok too.

zetafunc.
2012-10-27 09:20:51

reconsideryouranswer wrote:

anonimnystefy wrote:

i was wondering what derivatives of |x| and sgn(x) are.
i thought of something but i got that they were sgn(x) and 0
respectfully.i think something is wrong here.What?

















Sorry for the bump, but could you not just say






?

anonimnystefy
2011-11-13 12:12:46

nice explanation! thanks rya!

i guess sgn(x) can be done similairly.

reconsideryouranswer
2011-11-13 12:10:15

anonimnystefy wrote:

i was wondering what derivatives of |x| and sgn(x) are.
i thought of something but i got that they were sgn(x) and 0
respectfully.i think something is wrong here.What?

















anonimnystefy
2011-11-13 10:16:14

ok thanks for the help,and could sure use luck!I'm not sure about that brilliantly!

bob bundy
2011-11-13 08:34:58

hi Stefy

Yes, that's what I think.

Good luck in the exams (not that you need it .. I'm sure you'll do brilliantly)

Bob

anonimnystefy
2011-11-13 06:45:55

hi bob

yes,i have been occupied by school and my subjects.this was a crazy week.i'm glad it's over,but there is next week exams and i have physics, analysis and in the one after i have geometry and programming. very busy weeks! smile

anyway,if i gave the restriction x<>0 then would my answers be correct?

bob bundy
2011-11-12 19:43:09

hi Stefy,

Haven't 'spoken' to you in a while.  Hope you are well.   smile

Derivatives have to be 'well defined'.  Specifically, this breaks down where the left limit isn't the same as the right limit.

So neither have a  defined value at x = 0.

For |x|           the deriv = 1 for x > 0       and         -1 for x < 0.

How are you defining sgn(x) ?

If you mean         1 when x > 0         and          -1 when X < 0,         then zero is correct. 

As this function is discontinuous at x = 0,   I think you must exclude x = 0 from this derivative even though the value is the same either side of zero.

Bob

anonimnystefy
2011-11-12 10:42:00

hi guys

i was wondering what derivatives of |x| and sgn(x) are.i thought of something but i got that they were sgn(x) and 0 respectfully.i think something is wrong here.What?

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