log

C++ Reference

log
Syntax:
  #include <math.h>
  double log( double num );

The function log() returns the natural (base e) logarithm of num. There's a domain error if num is negative, a range error if num is zero.

In order to calculate the logarithm of x to an arbitrary base b, you can use:

  double answer = log(x) / log(b);
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