Change of Base of Logarithm/Base e to Base 10/Form 2

Theorem
Let $\log_{10} x$ be the common (base $10$) logarithm of $x$.

Let $\ln x$ be the natural (base $e$) logarithm of $x$.

Then:
 * $\log_{10} x = \dfrac {\ln x} {\ln 10} = \dfrac {\ln x} {2 \cdotp 30258 \, 50929 \, 94 \ldots}$

Proof
From Change of Base of Logarithm:
 * $\log_a x = \dfrac {\log_b x} {\log_b a}$

Substituting $a = 10$ and $b = e$ gives:
 * $\log_{10} x = \dfrac {\ln x} {\ln 10}$

as by definition of $\ln x$:
 * $\ln x := \log_e x$

The Natural Logarithm of 10:
 * $\ln 10 = 2 \cdotp 30258 \, 50929 \, 94 \ldots$

can then be calculated or looked up.