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Topic: new tutor here
Replies: 151   Last Post: Jul 17, 2013 4:09 AM

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Dave L. Renfro

Posts: 4,518
Registered: 12/3/04
Re: new tutor here
Posted: Jun 21, 2013 5:44 PM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

Joe Niederberger wrote (in part):

http://mathforum.org/kb/message.jspa?messageID=9139298

>> Here's the pic:
>> Simply the log (ln) curve, with points where it intersects
>> (e,1) and (pi,log(pi)) noted.


Robert Hansen wrote:

http://mathforum.org/kb/message.jspa?messageID=9139925

> Ok, so let me ask you: How does your picture show that e^pi > pi^e?

I don't know what Joe's explanation is (when more hand-holding
details are included), although I haven't tried very hard to
figure it out. However, one way is to note that the numerical
order of e^pi and pi^e is unchanged if e^pi is replaced with
(ln e)/e and pi^e is replaced with (ln pi)/pi. This follows
from the fact that the natural logarithm function is strictly
increasing:

e^pi # pi^e [# is < or = or >, whichever is correct]

is equivalent to

ln(e^pi) # ln(pi^e)

which is equivalent to

pi*(ln e) # e*(ln pi)

which is equivalent to

(ln e)/e # (ln pi)/pi [Note: This suggests considering f(x) = (ln x)/x.]

which is equivalent to

1/e # (ln pi)/pi

Off hand, I don't see how we can tell by precalculus methods
which of 1/e and (ln pi)/pi is greater (or equivalently, which
of pi/e and (ln pi) is greater), but I do know that taking the
derivative of f(x) = (ln x)/x and setting the result equal to
zero (and paying attention to where the derivative is positive
and where the derivative is negative), we find that f(x) has a
maximum (local and global) at x = e. Thus,

(ln e)/e > (ln pi)/pi

and so we get

e^pi > pi^e

See the following web page for several proofs of this inequality,
including a usefully labeled graph of f(x) = (ln x)/x.

http://math.stackexchange.com/questions/7892/comparing-pie-and-e-pi

Dave L. Renfro


Date Subject Author
6/12/13
Read new tutor here
Michael Mossey
6/12/13
Read Re: new tutor here
Wayne Bishop
6/12/13
Read Re: new tutor here
Michael Mossey
6/13/13
Read Re: new tutor here
Wayne Bishop
6/13/13
Read Re: new tutor here
Dave L. Renfro
6/13/13
Read Re: new tutor here
Joe Niederberger
6/14/13
Read Re: new tutor here
Robert Hansen
6/14/13
Read Re: new tutor here
Joe Niederberger
6/14/13
Read Re: new tutor here
Robert Hansen
6/14/13
Read Re: new tutor here
Joe Niederberger
6/14/13
Read Re: new tutor here
Robert Hansen
6/14/13
Read Re: new tutor here
Joe Niederberger
6/14/13
Read Re: new tutor here
Robert Hansen
6/15/13
Read Re: new tutor here
Louis Talman
6/14/13
Read Re: new tutor here
Michael Mossey
6/15/13
Read Re: new tutor here
Robert Hansen
6/14/13
Read Re: new tutor here
GS Chandy
6/16/13
Read Re: new tutor here
GS Chandy
6/15/13
Read Re: new tutor here
Louis Talman
6/15/13
Read Re: new tutor here
Joe Niederberger
6/16/13
Read Re: new tutor here
Robert Hansen
6/15/13
Read Re: new tutor here
Pam
6/16/13
Read Re: new tutor here
Robert Hansen
6/15/13
Read Re: new tutor here
Pam
6/16/13
Read Re: new tutor here
Wayne Bishop
6/16/13
Read Re: new tutor here
Joe Niederberger
6/16/13
Read Re: new tutor here
Robert Hansen
6/16/13
Read Re: new tutor here
Joe Niederberger
6/17/13
Read Re: new tutor here
Robert Hansen
6/16/13
Read Re: new tutor here
Michael Mossey
6/17/13
Read Re: new tutor here
GS Chandy
6/17/13
Read Re: new tutor here
GS Chandy
6/17/13
Read Re: new tutor here
Pam
6/17/13
Read Re: new tutor here
Robert Hansen
6/17/13
Read Re: new tutor here
Pam
6/17/13
Read Re: new tutor here
Robert Hansen
6/17/13
Read Re: new tutor here
Pam
6/17/13
Read Re: new tutor here
Pam
6/17/13
Read Re: new tutor here
Joe Niederberger
6/17/13
Read Re: new tutor here
Robert Hansen
6/17/13
Read Re: new tutor here
Joe Niederberger
6/17/13
Read Re: new tutor here
Joe Niederberger
6/18/13
Read Re: new tutor here
Robert Hansen
6/17/13
Read Re: new tutor here
GS Chandy
6/18/13
Read Re: new tutor here
GS Chandy
6/18/13
Read Re: new tutor here
GS Chandy
6/18/13
Read Re: new tutor here
GS Chandy
6/18/13
Read Re: new tutor here
Joe Niederberger
6/18/13
Read Re: new tutor here
Robert Hansen
6/18/13
Read Re: new tutor here
Joe Niederberger
6/18/13
Read Re: new tutor here
Joe Niederberger
6/18/13
Read Re: new tutor here
Robert Hansen
6/18/13
Read Re: new tutor here
Joe Niederberger
6/18/13
Read Re: new tutor here
Joe Niederberger
6/18/13
Read Re: new tutor here
Robert Hansen
6/18/13
Read Re: new tutor here
Robert Hansen
6/18/13
Read Re: new tutor here
Joe Niederberger
6/19/13
Read Re: new tutor here
Robert Hansen
6/19/13
Read Re: new tutor here
Robert Hansen
6/21/13
Read Re: new tutor here
Wayne Bishop
6/21/13
Read Re: new tutor here
Wayne Bishop
6/19/13
Read Re: new tutor here
Joe Niederberger
6/19/13
Read Re: new tutor here
Robert Hansen
6/19/13
Read Re: new tutor here
Joe Niederberger
6/19/13
Read Re: new tutor here
Robert Hansen
6/19/13
Read Re: new tutor here
Joe Niederberger
6/19/13
Read Re: new tutor here
Robert Hansen
6/19/13
Read Re: new tutor here
Joe Niederberger
6/19/13
Read Re: new tutor here
Robert Hansen
6/19/13
Read Re: new tutor here
Robert Hansen
6/19/13
Read Re: new tutor here
Joe Niederberger
6/19/13
Read Re: new tutor here
Joe Niederberger
6/19/13
Read Re: new tutor here
Joe Niederberger
6/19/13
Read Re: new tutor here
Robert Hansen
6/21/13
Read Re: new tutor here
Joe Niederberger
6/21/13
Read Re: new tutor here
Robert Hansen
6/21/13
Read Re: new tutor here
Joe Niederberger
6/21/13
Read Re: new tutor here
Robert Hansen
6/21/13
Read Re: new tutor here
Joe Niederberger
6/21/13
Read Re: new tutor here
Robert Hansen
6/21/13
Read Re: new tutor here
Joe Niederberger
6/21/13
Read Re: new tutor here
Joe Niederberger
6/21/13
Read Re: new tutor here
Dave L. Renfro
6/22/13
Read Re: new tutor here
Robert Hansen
6/22/13
Read Re: new tutor here
Robert Hansen
6/22/13
Read Re: new tutor here
Joe Niederberger
6/22/13
Read Re: new tutor here
Robert Hansen
6/22/13
Read Re: new tutor here
Robert Hansen
6/23/13
Read Re: new tutor here
Joe Niederberger
6/23/13
Read Re: new tutor here
Robert Hansen
6/23/13
Read Re: new tutor here
Robert Hansen
6/23/13
Read Re: new tutor here
Joe Niederberger
6/23/13
Read Re: new tutor here
Robert Hansen
6/24/13
Read Re: new tutor here
Robert Hansen
6/24/13
Read Re: new tutor here
Joe Niederberger
6/24/13
Read Re: new tutor here
Joe Niederberger
6/24/13
Read Re: new tutor here
Joe Niederberger
6/25/13
Read Re: new tutor here
GS Chandy
7/10/13
Read Re: new tutor here
Dave L. Renfro
7/10/13
Read Re: new tutor here
Robert Hansen
7/10/13
Read Re: new tutor here
Joe Niederberger
7/10/13
Read Re: new tutor here
Robert Hansen
7/10/13
Read Re: new tutor here
Robert Hansen
7/10/13
Read Re: new tutor here
Robert Hansen
7/11/13
Read Re: new tutor here
Joe Niederberger
7/11/13
Read Re: new tutor here
Robert Hansen
7/11/13
Read Re: new tutor here
Joe Niederberger
7/11/13
Read Re: new tutor here
Robert Hansen
7/11/13
Read Re: new tutor here
Robert Hansen
7/11/13
Read Re: new tutor here
GS Chandy
7/11/13
Read Re: new tutor here
Joe Niederberger
7/11/13
Read Re: new tutor here
Robert Hansen
7/11/13
Read Re: new tutor here
Robert Hansen
7/11/13
Read Re: new tutor here
Louis Talman
7/11/13
Read Re: new tutor here
Robert Hansen
7/12/13
Read Re: new tutor here
Wayne Bishop
7/12/13
Read Re: new tutor here
Louis Talman
7/12/13
Read Re: new tutor here
Wayne Bishop
7/12/13
Read Re: new tutor here
Robert Hansen
7/12/13
Read Re: new tutor here
Gary Tupper
7/12/13
Read Re: new tutor here
Wayne Bishop
7/12/13
Read Re: new tutor here
Louis Talman
7/11/13
Read Re: new tutor here
Joe Niederberger
7/11/13
Read Re: new tutor here
Robert Hansen
7/11/13
Read Re: new tutor here
Joe Niederberger
7/11/13
Read Re: new tutor here
GS Chandy
7/12/13
Read Re: new tutor here
Wayne Bishop
7/12/13
Read Re: new tutor here
Joe Niederberger
7/12/13
Read Re: new tutor here
Wayne Bishop
7/12/13
Read Re: new tutor here
GS Chandy
7/12/13
Read Re: new tutor here
Joe Niederberger
7/13/13
Read Re: new tutor here
Robert Hansen
7/13/13
Read Re: new tutor here
GS Chandy
7/13/13
Read Re: new tutor here
Joe Niederberger
7/13/13
Read Re: new tutor here
Wayne Bishop
7/13/13
Read Re: new tutor here
Robert Hansen
7/13/13
Read Re: new tutor here
Robert Hansen
7/13/13
Read Re: new tutor here
Peter Duveen
7/14/13
Read Re: new tutor here
Joe Niederberger
7/14/13
Read Re: new tutor here
Joe Niederberger
7/14/13
Read Re: new tutor here
Joe Niederberger
7/14/13
Read Re: new tutor here
Robert Hansen
7/14/13
Read Re: new tutor here
GS Chandy
7/15/13
Read Re: new tutor here
Wayne Bishop
7/15/13
Read Re: new tutor here
Joe Niederberger
7/15/13
Read Re: new tutor here
Robert Hansen
7/15/13
Read Re: new tutor here
Peter Duveen
7/15/13
Read Re: new tutor here
Joe Niederberger
7/16/13
Read Re: new tutor here
GS Chandy
7/16/13
Read Re: new tutor here
Wayne Bishop
7/16/13
Read Re: new tutor here
GS Chandy
7/17/13
Read Re: new tutor here
GS Chandy

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