30.7.5 Eccentricity Unifies the Three Curves
Core ideaWith the same single e: less than 1 is an ellipse, equal to 1 is a parabola, and greater than 1 is a hyperbola.
Module goal. Introduce the parabola and, through equal point-line distance and eccentricity, thread all three curves into one system, wrapping up the coordinate method.