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  2. Unit vector - Wikipedia

    en.wikipedia.org/wiki/Unit_vector

    [1] [2] The term normalized vector is sometimes used as a synonym for unit vector. A unit vector is often used to represent directions, such as normal directions. Unit vectors are often chosen to form the basis of a vector space, and every vector in the space may be written as a linear combination form of unit vectors.

  3. Quaternion - Wikipedia

    en.wikipedia.org/wiki/Quaternion

    For two elements a 1 + b 1 i + c 1 j + d 1 k and a 2 + b 2 i + c 2 j + d 2 k, their product, called the Hamilton product (a 1 + b 1 i + c 1 j + d 1 k) (a 2 + b 2 i + c 2 j + d 2 k), is determined by the products of the basis elements and the distributive law. The distributive law makes it possible to expand the product so that it is a sum of ...

  4. Quaternions and spatial rotation - Wikipedia

    en.wikipedia.org/wiki/Quaternions_and_spatial...

    By inserting those vectors and angles into the formula for q above, one finds that if q represents the first rotation, −q represents the second rotation. This is a geometric proof that conjugation by q and by −q must produce the same rotational transformation matrix.

  5. Levi-Civita symbol - Wikipedia

    en.wikipedia.org/wiki/Levi-Civita_symbol

    The formula is valid for all index values, and for any n (when n = 0 or n = 1, this is the empty product). However, computing the formula above naively has a time complexity of O(n 2), whereas the sign can be computed from the parity of the permutation from its disjoint cycles in only O(n log(n)) cost.

  6. Vector calculus identities - Wikipedia

    en.wikipedia.org/wiki/Vector_calculus_identities

    As the name implies, the divergence is a (local) measure of the degree to which vectors in the field diverge. The divergence of a tensor field of non-zero order k is written as ⁡ =, a contraction of a tensor field of order k − 1. Specifically, the divergence of a vector is a scalar.

  7. History of quaternions - Wikipedia

    en.wikipedia.org/wiki/History_of_quaternions

    In mathematics, quaternions are a non-commutative number system that extends the complex numbers.Quaternions and their applications to rotations were first described in print by Olinde Rodrigues in all but name in 1840, [1] but independently discovered by Irish mathematician Sir William Rowan Hamilton in 1843 and applied to mechanics in three-dimensional space.

  8. Classical Hamiltonian quaternions - Wikipedia

    en.wikipedia.org/wiki/Classical_Hamiltonian...

    Hamilton defined a quaternion as the quotient of two directed lines in tridimensional space; [1] or, more generally, as the quotient of two vectors. [2] A quaternion can be represented as the sum of a scalar and a vector. It can also be represented as the product of its tensor and its versor.

  9. Seven-dimensional cross product - Wikipedia

    en.wikipedia.org/wiki/Seven-dimensional_cross...

    In zero dimensions there is only the zero vector, while in one dimension all vectors are parallel, so in both these cases the product must be identically zero. The restriction to 0, 1, 3 and 7 dimensions is related to Hurwitz's theorem, that normed division algebras are only possible in 1, 2, 4 and 8 dimensions. The cross product is formed from ...