[Pdx-pm] log base 10

Tkil tkil at scrye.com
Thu Apr 8 18:10:46 CDT 2004

>>>>> "DS" == darthsmily  <darthsmily at verizon.net> writes:

DS> Log10 = Log(number) / 2.30258509299405

For the people who wonder where the magic number comes from: the
logarithm of x in base b can be calculated by dividing the natural log
of x by the natural log of b.  In formula form (so far as ascii art

           ln x
   log x = ----
      b    ln b

I don't remember enough math to tell you what the appropriate domains
would be, but for simple calculations, this should be sufficient.

In this case, b is 10, so we have

   log10(x) = ln(x) / ln(10)

And ln(10) is 2.30258509299404568402, at least according to M_LN10 in
/usr/include/math.h.  :)


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