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The function f (x) = log_{10} x is called the common logarithmic function. The common log function is often written as f (x) = log x -- when log is written without a base, the base is assumed to be 10. The " log " button on most calculators means log_{10} .
Examples:
log1000 = 3
.
log0.01 = - 2
.
log45 1.653
(using a calculator).
The number 2.71828… occurs often in mathematics and nature. For this reason, it is given a special name: e . Like Π , e is a number that mathematicians use often, and it is an irrational number, so it does not repeat or terminate. e has been calculated to many decimal places, but it is often rounded to e 2.718281828 .
e ^{1} | 2.71828 | ||
e ^{2} | 7.38906 | ||
e ^{3} | 20.0855 | ||
e ^{4} | 54.5982 | ||
… |
The function f (x) = log_{e} x is called the natural logarithmic function. The natural log function is often abbreviated f (x) = ln x --this is the way it appears on most calculators. ln e ^{x} = x and e ^{ln x} = x .
Examples:
lne
^{4} = 4
.
ln
= - 2
.
ln62 4.1271
.
ln230 5.4381
.
ln0.04 - 3.2189
.