\begin{definition}[Definition:Lemniscate of Bernoulli/Major Axis]
Consider the '''lemniscate of Bernoulli''' defined as the locus $M$ described by the equation:
:$P_1 M \times P_2 M = \paren {\dfrac {P_1 P_2} 2}^2$
:630px
The line $P_1 P_2$ is the '''major axis''' of the lemniscate.
Category:Definitions/Lemniscates
\end{definition}