21.4.3 Logarithmic Expressions The term log is an abbreviation
of logarithm. A system of logarithms may be based on any number,
although logarithmic systems based on the numbers 10, 2, and the
irrational number e are most common. The base should be
subscripted and follow the word log. In the following examples,
note that logarithms are always computed from exponents of the
number that forms their basis. log10 1000 = 3 (because 1000 =
103) log2 8 = 3 (because 8 = 23) Logarithms based on e (which is
approximately 2.71) are called natural logarithms and are often
represented as ln. ln 2.71 = 1 The terms “ex” and “exp x” are
identical in meaning and are interchangeable. The latter is
preferable for constructions involving additional subscripts or
superscripts. For instance, “exp (x3 − 1)” is identical to but
the former is preferred because it is easier to set and to read.