Ellipses Topic 7.4
Definitions • Ellipse: set of all points where the sum of the distances from the foci is constant • Major Axis: axis on which the foci lie; the longer axis of symmetry • Minor Axis: the shorter axis of symmetry
Two Standard Equations • Horizontal Ellipse: • Foci: • Vertical Ellipse: • Foci:
Writing in Standard Form • Complete the square for both the x-terms and y-terms and move the constant to the other side of the equation • Divide all terms by the constant
Example: Group terms Complete the square Simplify each group Divide by constant
Graphing the ellipse • Put equation in standard form • Graph the center (h, k) • Graph the foci (look at the equation to determine your direction) • Graph a units and –a units from the center to get the end points (horizontally if under x, vertically if under y) • Connect the end points!
Example: 1) Graph Center 2) Graph Foci 3) Graph Endpoints 4) Graph Ellipse