Definition:Apotome/Fifth Apotome

Definition
Let $a, b \in \R_{>0}$ be two (strictly) positive real numbers such that $a - b$ is an apotome.

Then $a - b$ is a fifth apotome :
 * $(1): \quad b \in \Q$
 * $(2): \quad \dfrac {\sqrt {a^2 - b^2}} a \notin \Q$

where $\Q$ denotes the set of rational numbers.



Example
When $a = \sqrt {13}$ and $b = 3$:

Therefore $\sqrt {13} - 3$ is a fifth apotome.

Also see

 * Definition:First Apotome
 * Definition:Second Apotome
 * Definition:Third Apotome
 * Definition:Fourth Apotome
 * Definition:Sixth Apotome