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Conics: Parabolas. Parabolas:. The set of all points equidistant from a fixed line called the directrix and a fixed point called the focus . The vertex is the point midway between the focus and the directrix . The line that connects the vertex and the focus is the axis of symmetry.
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Parabolas: • The set of all points equidistant from a fixed line called the directrix and a fixed point called the focus. • The vertex is the point midway between the focus and the directrix. • The line that connects the vertex and the focus is the axis of symmetry.
The standard form equation of a parabola with vertex at (h, k) is The first equation is for a parabola that opens up or down. The second equation is for a parabola that opens left or right.
If the equation is • The focus is the point . • The directrix is the line. • The axis of symmetry is parallel to the y-axis (vertical).
If the equation is • The focus is the point . • The directix is the line . • The axis of symmetry is parallel to the x-axis (horizontal).
Latus Rectum • The latus rectum is a line segment through the focus, parallel to the directrix. • The endpoints of the latusrectum are each a distance of 2a from the focus.
Ex. 1 Find the vertex, focus and directrix of the parabola. Graph the equation. a)
Ex.2 Write the equation of the parabola. a) Vertex: (0, 0), focus: (-4, 0)
c) Directrix: x = -4, focus: (2, 4) Hint: start with a sketch of the graph.
Ex. 3 Write the equation of the parabola with the given vertex and point on the parabola. • a) Vertex: (1, 0) Point: (0, 1)