Math Is Fun Forum

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Need help with those logarithms.

Need help about this problem. I almost got it but I must have messed it up somewhere.
We have a system of two eqations:

Last edited by anonimnystefy (2011-05-26 04:25:00)

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“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
The knowledge of some things as a function of age is a delta function.

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: Need help with those logarithms.

Hi anonimnystefy,

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"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Need help with those logarithms.

thought so but it's different in the solution. maybe the solution is wrong.thanks anyway.

what about this:

Last edited by anonimnystefy (2011-05-26 04:36:59)

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“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
The knowledge of some things as a function of age is a delta function.

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: Need help with those logarithms.

When your final answer fits in the equation you needn't worry!

Hmmm, square root of a logarithm is a bit counter-intuitive to me. I'll try anyway.

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"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

soroban

Member

Registered: 2007-03-09

Posts: 452

Re: Need help with those logarithms.

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I see that gAr beat me to it . . . *sigh*

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: Need help with those logarithms.

Hi soroban,

Your solution is much more clear than I can possibly explain.
It would definitely help beginners to logarithms.

Hi anonimnystefy,

---

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Need help with those logarithms.

hi gAr and soroban,
you helped me a lot.
but i have to ask you what the logarithm of a negative number is if the baseof the algorithm is not e=2,7.

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“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
The knowledge of some things as a function of age is a delta function.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: Need help with those logarithms.

hi anonimnystefy

The normal graph of logarithmic functions would suggest that you cannot have the log of a negative.

But that hasn't stop mathematicians!  Just as with the square root of minus one it is posible to use complex numbers for this task.

see http://en.wikipedia.org/wiki/Complex_logarithm

When the others come back on line they'll probably fill in any details if you are left with questions.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: Need help with those logarithms.

Hi anonimnystefy,

You already know to take log of a negative number when base is e?
Anyway, an example:

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"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Need help with those logarithms.

hi gAr,
thanks for the explanation
i think that if the base is e then it would be:

---

“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
The knowledge of some things as a function of age is a delta function.

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: Need help with those logarithms.

Hi,

You're welcome.
Yes, but I use the convention log(a) to mean ln(a), if base is not mentioned.

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"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Need help with those logarithms.

hi gAr,
do you maybe know how the number e was found?

---

“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
The knowledge of some things as a function of age is a delta function.

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Need help with those logarithms.

---

“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
The knowledge of some things as a function of age is a delta function.

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: Need help with those logarithms.

Hi,

I only know e, its definition, haven't browsed much on its history...

And your infinite power doesn't converge: So answer is infinity.

I'm taking a break, see you later!

Last edited by gAr (2011-05-28 06:13:03)

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"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: Need help with those logarithms.

Hi anonimnystefy,

instead, try:

or

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"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."