Reciprocal of Logarithm

Theorem
Let $x, y \in \R_{> 0}$ be (strictly) positive real numbers.

Then:
 * $\dfrac 1 {\log_x y} = \log_y x$

Also presented as
This result can also be seen presented as:


 * $\paren {\log_x y} \paren {\log_y x} = 1$