Math Is Fun Forum

{7/3}

Member

Registered: 2013-02-11

Posts: 210

logarithm

prove that if r is real,then log r is real.

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There are 10 kinds of people in the world,people who understand binary and people who don't.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,621

Re: logarithm

prove that if r is real,then log r is real.

hhmmm.  That's going to be tough when r is a negative real number.

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

{7/3}

Member

Registered: 2013-02-11

Posts: 210

Re: logarithm

sorry forgot to say positive

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There are 10 kinds of people in the world,people who understand binary and people who don't.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,621

Re: logarithm

This time, I think it is down to the definition:

http://en.wikipedia.org/wiki/Logarithm

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

{7/3}

Member

Registered: 2013-02-11

Posts: 210

Re: logarithm

I want a proof that b for every positive b and n there is a real number x such that b^x=n

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There are 10 kinds of people in the world,people who understand binary and people who don't.