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Topics in Analytic Geometry. Pre Calc Chapter 9. Parabolas—9.1. Parabolas. Vertex The lowest or highest point of the graph (based on which way it opens) Axis of symmetry. Geometric Definition.
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Topics in Analytic Geometry Pre Calc Chapter 9
Parabolas • Vertex • The lowest or highest point of the graph (based on which way it opens) • Axis of symmetry
Geometric Definition • A parabola is the set of points in the plane equidistant from a fixed point F (the focus) and a fixed line l called the directrix
Analytic Geometry • Concerned with shapes, not necessarily functionality • Parabolas can open up • Parabolas can open down • Inverse
Parabola with Vertical Axis The Graph of the equation:is a parabola with the following: Vertex Focus Directrix Parabola opens up if or down if
Parabola with Horizontal Axis The Graph of the equation:is a parabola with the following: Vertex Focus Directrix Parabola opens right if or left if
Focal Diameter • Distance across the parabola along the line parallel to the directrix
Geometric Definition • An ellipse is the set of all points in the plane the sum of whose distances from two fixed points and is a constant. • These points are the foci
Ellipse Equation Vertices Major Axis Horizontal, length 2a Vertical, 2a Minor Axis Vertical, length 2b Horizontal, 2b Foci
Eccentricity • For the ellipse or the eccentricity, e, is the numberwhere and the eccentricity of every ellipse satisfies
Ellipses • Find the equation of the ellipse with foci and eccentricity
Geometric Definition • A hyperbola is the set of all points in the plane, the difference of whose distances from two fixed points and is a constant. • These are the foci of the hyperbola
Hyperbolas Equations Vertices Transverse Axis Horizontal, length 2a Asymptotes Foci
Hyperbolas Equations Vertices Transverse Axis Vertical, length 2b Asymptotes Foci
Sketching Hyperbolas • Sketch the Central Box • Sketch the asymptotes • Plot the vertices • Sketch the hyperbola • Smile
Hyperbolas • Find the equation of the hyperbola with vertices and foci
General Equation of a Conic • The graph of the equationWhere A and C are not both 0, is a conic or degenerate conic where the graph is: • A parabola if A or C is 0 • An ellipse if A and C have the same sign • Circle if A = C • A hyperbola is A and C have opposite signs
Degenerate Conic • Conic which simplifies to only 2 lines
Rotation of Axes • Recall… • Now…
Rotation of Axes Formula • Suppose the x- and y-axes in a coordinate plane are rotated through the acute angle to produce the X- and Y-axes. Then the coordinates (x,y) and (X,Y) of a point in the xy- and XY-panes are related as follows: x=Xcosφ-Ysinφ X=xcosφ+ysinφ y=Xsinφ+Ycosφ Y=-xsinφ+ycosφ
Rotation of Axes • If the coordinates are rotated 30 degrees, find the XY-coordinates of the point with xy-coordinates (2, -4)
Rotation of Axes • Rotate the coordinate axes through 45 degrees to show that the graph of the equation xy = 2 is a hyperbola
Polar Coordinates • Uses distances and directions to specify locations on the plane • Origin (Pole) • Polar Axis • Polar Coordinates