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  2. Parabola - Wikipedia

    en.wikipedia.org/wiki/Parabola

    Let the perpendicular to the line of symmetry, through the focus, intersect the parabola at a point T. Then (1) the distance from F to T is 2f, and (2) a tangent to the parabola at point T intersects the line of symmetry at a 45° angle. [13]: 26 Perpendicular tangents intersect on the directrix

  3. Intersection (geometry) - Wikipedia

    en.wikipedia.org/wiki/Intersection_(geometry)

    The red dot represents the point at which the two lines intersect. In geometry, an intersection is a point, line, or curve common to two or more objects (such as lines, curves, planes, and surfaces).

  4. Intersecting secants theorem - Wikipedia

    en.wikipedia.org/wiki/Intersecting_secants_theorem

    Next to the intersecting chords theorem and the tangent-secant theorem, the intersecting secants theorem represents one of the three basic cases of a more general theorem about two intersecting lines and a circle - the power of point theorem.

  5. Tangent–secant theorem - Wikipedia

    en.wikipedia.org/wiki/Tangent–secant_theorem

    Like the intersecting chords theorem and the intersecting secants theorem, the tangent-secant theorem represents one of the three basic cases of a more general theorem about two intersecting lines and a circle, namely, the power of point theorem.

  6. Envelope (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Envelope_(mathematics)

    The zero level set F(t 0,(x,y)) = 0 gives the equation of the tangent line to the parabola at the point (t 0,t 0 2). The equation t 2 – 2 tx + y = 0 can always be solved for y as a function of x and so, consider

  7. Conic section - Wikipedia

    en.wikipedia.org/wiki/Conic_section

    If the intersection point is double, the line is a tangent line. Intersecting with the line at infinity, each conic section has two points at infinity. If these points are real, the curve is a hyperbola; if they are imaginary conjugates, it is an ellipse; if there is only one double point, it is a parabola.

  8. Tangent lines to circles - Wikipedia

    en.wikipedia.org/wiki/Tangent_lines_to_circles

    But only a tangent line is perpendicular to the radial line. Hence, the two lines from P and passing through T 1 and T 2 are tangent to the circle C. Another method to construct the tangent lines to a point P external to the circle using only a straightedge: Draw any three different lines through the given point P that intersect the circle twice.

  9. Dupin indicatrix - Wikipedia

    en.wikipedia.org/wiki/Dupin_indicatrix

    For parabolic points, where the Gaussian curvature is zero, the intersection will form two parallel lines. The direction of those two lines are the same as the asymptotic directions. In particular, the indicatrix of each point on a developable surface is a pair of lines parallel to the generatrix.