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  2. Parabola - Wikipedia

    en.wikipedia.org/wiki/Parabola

    An inclined cross-section of the cone, shown in pink, is inclined from the axis by the same angle θ, as the side of the cone. According to the definition of a parabola as a conic section, the boundary of this pink cross-section EPD is a parabola. A cross-section perpendicular to the axis of the cone passes through the vertex P of the parabola.

  3. Purlin - Wikipedia

    en.wikipedia.org/wiki/Purlin

    A purlin (or historically purline, purloyne, purling, perling) is a longitudinal, horizontal, structural member in a roof. In traditional timber framing there are three basic types of purlin: purlin plate, principal purlin, and common purlin. Purlins also appear in steel frame construction. Steel purlins may be painted or greased for protection ...

  4. Ellipse - Wikipedia

    en.wikipedia.org/wiki/Ellipse

    Ellipses are the closed type of conic section: a plane curve tracing the intersection of a cone with a plane (see figure). Ellipses have many similarities with the other two forms of conic sections, parabolas and hyperbolas, both of which are open and unbounded. An angled cross section of a right circular cylinder is also an ellipse.

  5. Shoelace formula - Wikipedia

    en.wikipedia.org/wiki/Shoelace_formula

    The shoelace formula, also known as Gauss's area formula and the surveyor's formula, [1] is a mathematical algorithm to determine the area of a simple polygon whose vertices are described by their Cartesian coordinates in the plane. [2] It is called the shoelace formula because of the constant cross-multiplying for the coordinates making up the ...

  6. Paraboloid - Wikipedia

    en.wikipedia.org/wiki/Paraboloid

    Paraboloid. In geometry, a paraboloid is a quadric surface that has exactly one axis of symmetry and no center of symmetry. The term "paraboloid" is derived from parabola, which refers to a conic section that has a similar property of symmetry. Every plane section of a paraboloid by a plane parallel to the axis of symmetry is a parabola.

  7. List of second moments of area - Wikipedia

    en.wikipedia.org/wiki/List_of_second_moments_of_area

    The second moment of area, also known as area moment of inertia, is a geometrical property of an area which reflects how its points are distributed with respect to an arbitrary axis. The unit of dimension of the second moment of area is length to fourth power, L 4, and should not be confused with the mass moment of inertia.

  8. Cross section (geometry) - Wikipedia

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

    A cross-section view of a compression seal. In geometry and science, a cross section is the non-empty intersection of a solid body in three-dimensional space with a plane, or the analog in higher- dimensional spaces. Cutting an object into slices creates many parallel cross-sections. The boundary of a cross-section in three-dimensional space ...

  9. Shallow water equations - Wikipedia

    en.wikipedia.org/wiki/Shallow_water_equations

    For example, for a rectangular cross section, with constant channel width B and channel bed elevation z b, the cross sectional area is: A = B (ζ − z b) = B h. The instantaneous water depth is h(x,t) = ζ(x,t) − z b (x), with z b (x) the bed level (i.e. elevation of the lowest point in the bed above datum, see the cross-section figure).