The logarithm of the reciprocal of a number, equal to the negative of the logarithm of the number itself,
Cologarithm
See also
Antilogarithm, LogarithmExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Cologarithm." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Cologarithm.html