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#1 2013-02-25 08:33:05

genericname
Member
Registered: 2012-05-16
Posts: 52

Log question

(2*(n/2)*lg(n/2)) + n

= (n*lg(n/2))+n

= n*(lg n - 1) + n

How does (n*lg(n/2))+n simplify to n*(lg n - 1) + n? What happened to the n/2 that was inside? It has been a while since I last worked with log.

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#2 2013-02-25 08:50:27

bobbym
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From: Bumpkinland
Registered: 2009-04-12
Posts: 81,656

Re: Log question

Hi;

Is this the problem?

Last edited by bobbym (2013-02-25 08:51:47)


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

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#3 2013-02-25 08:58:06

genericname
Member
Registered: 2012-05-16
Posts: 52

Re: Log question

Yeah.

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#4 2013-02-25 10:10:06

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,656

Re: Log question

I am getting:

Last edited by bobbym (2013-02-25 10:10:52)


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Online

#5 2013-02-25 13:40:36

anonimnystefy
Real Member
From: The Foundation
Registered: 2011-05-23
Posts: 14,840

Re: Log question

Hi genericname

lg(a/b)=lg(a)-lg(b) for any a and b for which the expression is defined.

So, lg(n/2)=lg(n)-lg(2)=lg(n)-1, assuming the logarithm is with base 2.


“Here lies the reader who will never open this book. He is forever dead.

“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

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#6 2013-02-25 14:27:50

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,656

Re: Log question

Why would the log be to the base two?


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Online

#7 2013-02-25 14:41:10

anonimnystefy
Real Member
From: The Foundation
Registered: 2011-05-23
Posts: 14,840

Re: Log question

Because then the step makes sense. We will have have to wait for the OP's answer.

And besides, the use of n and lg reminds me of comp. analysis.

Last edited by anonimnystefy (2013-02-25 14:42:40)


“Here lies the reader who will never open this book. He is forever dead.

“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

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#8 2013-02-25 16:31:10

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 81,656

Re: Log question

A very good answer!


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Online

#9 2013-02-26 03:44:16

genericname
Member
Registered: 2012-05-16
Posts: 52

Re: Log question

Ah, thank you. It was base 2, sorry for the confusion.

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#10 2013-02-26 06:19:58

anonimnystefy
Real Member
From: The Foundation
Registered: 2011-05-23
Posts: 14,840

Re: Log question

No problem and you're welcome!


“Here lies the reader who will never open this book. He is forever dead.

“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

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