AS/A2 Pure 4 Pure 6

P5 Topic 1: Coordinate Systems
The ellipse 2
Move point d left and right between x=0 and x=1 to view the ellipse that has an eccentricity equal to the x coordiinate of d.

Summary the green curve is an ellipse the point f is a focus of the ellipse, and the red line is a directrix of the ellipse. the eccentricity, e, is given by the x-coordinate of d. The coordinates of f are (e,0). The directrix is at x = 1/e all ellipses have an eccentricity between 0 and 1 Typically, an ellipse has equation: Its eccentricity, e, is found from: The directrices are at: The foci are at (±ae,0) The Plane Graphic Calculator java applet