Log
Function 
Log(value)
Log(value, base)

Log is included by default in each file as part of the Math library.
See also:
Use
The Log() function returns the logarithm of a number. By default, it uses base 10, but the base can be given as the second input.
Log() inputs must be unitless, as units aren't compatible with taking logarithms.
Log() is compatible with complex numbers.
Examples
Log(100) = 2
Log(32, 2) = 5
Log(10i) = 1 + 0.682i