2.3 Common Logarithm
The common logarithm is the logarithm with a base of 10. It is written as log10 or simply as log (when no base is mentioned, it is usually assumed to be base 10).
For example:
101=10⟺log10=1
102=100⟺log100=2
103=1000⟺log1000=3and so on.
10−1=101=0.1⟺log0.1=−1
10−2=1001=0.01⟺log0.01=−2
10−3=10001=0.001⟺log0.001=−3and so on.
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History
English mathematician Henry Briggs extended Napier's work and developed the common logarithm. He also introduced logarithmic table.