polar coordinate

(noun)

a two-dimensional coordinate system in which each point on a plane is determined by a distance from a fixed point and an angle from a fixed direction

Examples of polar coordinate in the following topics:

  • Double Integrals in Polar Coordinates

    • In $R^2$, if the domain has a cylindrical symmetry and the function has several particular characteristics, you can apply the transformation to polar coordinates, which means that the generic points $P(x, y)$ in Cartesian coordinates switch to their respective points in polar coordinates.
    • The polar coordinates $r$ and $\varphi$ can be converted to the Cartesian coordinates $x$ and $y$ by using the trigonometric functions sine and cosine:
    • The Cartesian coordinates $x$ and $y$ can be converted to polar coordinates $r$ and $\varphi$ with $r \geq 0$ and $\varphi$ in the interval $(−\pi, \pi]$:
    • Particularly in this case, you can see that the representation of the function f became simpler in polar coordinates.
    • This figure illustrates graphically a transformation from cartesian to polar coordinates
  • Polar Coordinates

    • Polar coordinates define the location of an object in a plane by using a distance and an angle from a reference point and axis.
    • Such definitions are called polar coordinates.
    • Polar coordinates in $r$ and $\theta$ can be converted to Cartesian coordinates $x$ and $y$.
    • A set of polar coordinates.
    • Use a polar coordinate to define a point with $r$ (distance from pole), and $\theta$(angle between axis and ray)
  • Conic Sections in Polar Coordinates

    • Conic sections are sections of cones and can be represented by polar coordinates.
    • In polar coordinates, a conic section with one focus at the origin is given by the following equation:
  • Area and Arc Length in Polar Coordinates

    • Area and arc length are calculated in polar coordinates by means of integration.
    • Since it can be very difficult to measure the length of an arc linearly, the solution is to use polar coordinates.
    • Using polar coordinates allows us to integrate along the length of the arc in order to compute its length.
    • To find the area enclosed by the arcs and the radius and polar angles, you again use integration.
    • Evaluate arc segment area and arc length using polar coordinates and integration
  • Arc Length and Speed

    • Obviously some cases require polar coordinates instead of Cartesian.
    • In polar coordinates:
  • Cylindrical and Spherical Coordinates

    • While Cartesian coordinates have many applications, cylindrical and spherical coordinates are useful when describing objects or phenomena with specific symmetries.
    • Then the $z$ coordinate is the same in both systems, and the correspondence between cylindrical $(\rho,\varphi)$ and Cartesian $(x,y)$ are the same as for polar coordinates, namely $x = \rho \cos \varphi; \, y = \rho \sin \varphi$.
    • A spherical coordinate system is a coordinate system for three-dimensional space where the position of a point is specified by three numbers: the radial distance of that point from a fixed origin, its polar angle measured from a fixed zenith direction, and the azimuth angle of its orthogonal projection on a reference plane that passes through the origin and is orthogonal to the zenith, measured from a fixed reference direction on that plane.
    • Spherical coordinates ($r$, $\theta$, $\varphi$) as often used in mathematics: radial distance $r$, azimuthal angle $\theta$, and polar angle $\varphi$.
    • A cylindrical coordinate system with origin $O$, polar axis $A$, and longitudinal axis $L$.
  • Change of Variables

    • To do so, the function must be adapted to the new coordinates.
    • Changing to cylindrical coordinates may be useful depending on the setup of problem.
  • Triple Integrals in Cylindrical Coordinates

    • When the function to be integrated has a cylindrical symmetry, it is sensible to integrate using cylindrical coordinates.
    • Also in switching to cylindrical coordinates, the $dx\, dy\, dz$ differentials in the integral become $\rho \, d\rho \,d\varphi \,dz$.
    • because the z component is unvaried during the transformation, the $dx\, dy\, dz$ differentials vary as in the passage in polar coordinates: therefore, they become: $\rho \, d\rho \,d\varphi \,dz$.
    • Finally, it is possible to apply the final formula to cylindrical coordinates:
    • Cylindrical coordinates are often used for integrations on domains with a circular base.
  • Three-Dimensional Coordinate Systems

    • The three-dimensional coordinate system expresses a point in space with three parameters, often length, width and depth ($x$, $y$, and $z$).
    • Each parameter is perpendicular to the other two, and cannot lie in the same plane. shows a Cartesian coordinate system that uses the parameters $x$, $y$, and $z$.
    • This is a three dimensional space represented by a Cartesian coordinate system.
    • The cylindrical coordinate system is like a mix between the spherical and Cartesian system, incorporating linear and radial parameters.
    • Identify the number of parameters necessary to express a point in the three-dimensional coordinate system
  • Triple Integrals in Spherical Coordinates

    • When the function to be integrated has a spherical symmetry, change the variables into spherical coordinates and then perform integration.
    • When the function to be integrated has a spherical symmetry, it is sensible to change the variables into spherical coordinates and then perform integration.
    • It's possible to use therefore the passage in spherical coordinates; the function is transformed by this relation:
    • Points on $z$-axis do not have a precise characterization in spherical coordinates, so $\theta$ can vary from $0$ to $2 \pi$.
    • Spherical coordinates are useful when domains in $R^3$ have spherical symmetry.
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