Definition:Lemniscate of Bernoulli/Major Axis

Definition
Consider the lemniscate of Bernoulli defined as the locus $M$ described by the equation:
 * $P_1 M \times P_2 M = \paren {\dfrac {P_1 P_2} 2}^2$


 * LemniscateOfBernoulli.png

The line $P_1 P_2$ is the major axis of the lemniscate.