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  2. Vector fields in cylindrical and spherical coordinates

    en.wikipedia.org/wiki/Vector_fields_in...

    Vectors are defined in cylindrical coordinates by (ρ, φ, z), where . ρ is the length of the vector projected onto the xy-plane,; φ is the angle between the projection of the vector onto the xy-plane (i.e. ρ) and the positive x-axis (0 ≤ φ < 2π),

  3. Theta function - Wikipedia

    en.wikipedia.org/wiki/Theta_function

    There are several closely related functions called Jacobi theta functions, and many different and incompatible systems of notation for them. One Jacobi theta function (named after Carl Gustav Jacob Jacobi) is a function defined for two complex variables z and τ, where z can be any complex number and τ is the half-period ratio, confined to the upper half-plane, which means it has a positive ...

  4. Spherical coordinate system - Wikipedia

    en.wikipedia.org/wiki/Spherical_coordinate_system

    To apply this to the present case, one needs to calculate how changes with each of the coordinates. In the conventions used, r = [ r sin ⁡ θ cos ⁡ φ r sin ⁡ θ sin ⁡ φ r cos ⁡ θ ] , x 1 = r , x 2 = θ , x 3 = φ . {\displaystyle \mathbf {r} ={\begin{bmatrix}r\sin \theta \,\cos \varphi \\r\sin \theta \,\sin \varphi \\r\cos \theta ...

  5. Trigonometric functions - Wikipedia

    en.wikipedia.org/wiki/Trigonometric_functions

    Basis of trigonometry: if two right triangles have equal acute angles, they are similar, so their corresponding side lengths are proportional.. In mathematics, the trigonometric functions (also called circular functions, angle functions or goniometric functions) [1] are real functions which relate an angle of a right-angled triangle to ratios of two side lengths.

  6. Rotation matrix - Wikipedia

    en.wikipedia.org/wiki/Rotation_matrix

    A more direct method, however, is to simply calculate the trace: the sum of the diagonal elements of the rotation matrix. Care should be taken to select the right sign for the angle θ to match the chosen axis: ⁡ = + ⁡,

  7. Rotation of axes in two dimensions - Wikipedia

    en.wikipedia.org/wiki/Rotation_of_axes_in_two...

    In mathematics, a rotation of axes in two dimensions is a mapping from an xy-Cartesian coordinate system to an x′y′-Cartesian coordinate system in which the origin is kept fixed and the x′ and y′ axes are obtained by rotating the x and y axes counterclockwise through an angle .

  8. Theta - Wikipedia

    en.wikipedia.org/wiki/Theta

    Theta (UK: / ˈ θ iː t ə /, US: / ˈ θ eɪ t ə /) uppercase Θ or ϴ; lowercase θ [note 1] or ϑ; Ancient Greek: θῆτα thē̂ta [tʰɛ̂ːta]; Modern: θήτα thī́ta) is the eighth letter of the Greek alphabet, derived from the Phoenician letter Teth 𐤈.

  9. Small-angle approximation - Wikipedia

    en.wikipedia.org/wiki/Small-angle_approximation

    [1] [2] One reason for this is that they can greatly simplify differential equations that do not need to be answered with absolute precision. There are a number of ways to demonstrate the validity of the small-angle approximations. The most direct method is to truncate the Maclaurin series for each of the trigonometric functions.