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The line perpendicular to the directrix and passing through the focus (that is, the line that splits the parabola through the middle) is called the "axis of symmetry". The point where the parabola intersects its axis of symmetry is called the "vertex" and is the point where the parabola is most sharply curved. The distance between the vertex ...
On a parabola, the sole vertex lies on the axis of symmetry and in a quadratic of the form: + + it can be found by completing the square or by differentiation. [2] On an ellipse, two of the four vertices lie on the major axis and two lie on the minor axis. [4]
An oval with a horizontal axis of symmetry Smooth closed convex curves with an axis of symmetry , such as an ellipse or Moss's egg , may sometimes be called ovals . [ 28 ] However, the same word has also been used to describe the sets for which each point has a unique line disjoint from the rest of the set, especially in the context of ovals in ...
The second term, / , gives the distance the roots are away from the axis of symmetry. If the parabola's vertex is on the -axis, then the corresponding equation has a single repeated root on the line of symmetry, and this distance term is zero; algebraically, the discriminant = .
Vertex and axis of symmetry in blue; Focus and directrix in pink; Visualisation of the complex roots of y = ax 2 + bx + c: the parabola is rotated 180° about its vertex (orange). Its x-intercepts are rotated 90° around their mid-point, and the Cartesian plane is interpreted as the complex plane (green). [3
From the point of view of projective geometry, an elliptic paraboloid is an ellipsoid that is tangent to the plane at infinity. Plane sections. The plane sections of an elliptic paraboloid can be: a parabola, if the plane is parallel to the axis, a point, if the plane is a tangent plane. an ellipse or empty, otherwise.
A three-dimensional version of parabolic coordinates is obtained by rotating the two-dimensional system about the symmetry axis of the parabolas. Parabolic coordinates have found many applications, e.g., the treatment of the Stark effect and the potential theory of the edges.
The semi-minor axis of an ellipse runs from the center of the ellipse (a point halfway between and on the line running between the foci) to the edge of the ellipse. The semi-minor axis is half of the minor axis. The minor axis is the longest line segment perpendicular to the major axis that connects two points on the ellipse's edge.