Definition:Bimedial/Second Bimedial

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Definition

Let $a, b \in \R_{>0}$ be in the forms:

$a = k^{1/4} \rho$
$b = \dfrac {\lambda^{1/2} \rho} {k^{1/4} }$

where:

$\rho$ is a rational number
$k$ is a rational number whose square root is irrational.
$\lambda$ is a rational number whose square root is irrational.


Then $a + b$ is a second bimedial.


In the words of Euclid:

If two medial straight lines commensurable in square only and containing a medial rectangle be added together, the whole is irrational; and let it be called a second bimedial straight line.

(The Elements: Book $\text{X}$: Proposition $38$)


Also see