Math Is Fun Forum

clooneyisagenius

Member

Registered: 2007-03-25

Posts: 56

Derivatives Help?

I'm working on some tougher derivatives.

1.

and

2.

, x is in the Reals

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For #1:
I tried to look at it two separate ways as x>0 and x<0.
I figured if x<0 then:

and thus

and if x>0 then:

and thus

Does this make sense? It seems too easy?

STUCK PRETTY MUCH COMPLETELY ON #2.

John E. Franklin

Member

Registered: 2005-08-29

Posts: 3,588

Re: Derivatives Help?

For #1,
You meant to say "if x>0" then x * x, so positive slope.
You meant to say " if x<0" then x * -x, so positive slope still.
Nice twisted parabola, like a cubic!!!
Nice work, just a typo.

For #2,
here's a graph, but you probably already have a graph.
and, it mirrors to the negative x the same positive way in the y-dimension.
http://img143.imageshack.us/img143/768/xsinesquaredxve3.png

On, #2, I noted that this function has
a similar graph, but perhaps not the same exactly.
y =  x/2 - x/2* cos(2* pi * x)
  versus your:   y =  x * sin(pi * x)*sin(pi * x)

Last edited by John E. Franklin (2008-02-07 17:30:53)

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igloo myrtilles fourmis

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Derivatives Help?

1.

2.

You know why

, don’t you?

Last edited by JaneFairfax (2008-02-07 21:50:11)