No Logarithm of a Negative Number

Date: 8/6/96 at 21:22:36
From: Anonymous
Subject: Logarithm of Negative Number

Hello,

Please tell me how to solve this problem:

log(-5) = ?

Date: 8/6/96 at 21:47:11
From: Doctor Robert
Subject: Re: Logarithm of Negative Number

Since a logarithm is an exponent, your question is equivalent to the 
question "What power of 10 gives me -5?"  

Positive exponents of 10 do not give negative results, and neither do 
negative exponents.  The answer is that you cannot find the logarithm 
of a negative number (at least, not over the set of real numbers).

I hope that this helps.

-Doctor Robert,  The Math Forum
 Check out our web site!  http://mathforum.org/dr.math/