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Logarithm of the base
Every logarithm of its own base is 1, so
ln e = 1 , log 10 = 1 , loga a = 1
Explanation
This follows directly from the definition of the logarithm, as
x = eln x ⇒ e = eln e = e1 ⇒ x = e
or
x = 10log x ⇒ 10 = 10log 10 = 101 ⇒ x = 10