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  2. Examples of groups - Wikipedia

    en.wikipedia.org/wiki/Examples_of_groups

    It is called the general linear group, and denoted GL n (R) or GL(n, R) (where R is the set of real numbers). Geometrically, it contains all combinations of rotations, reflections, dilations and skew transformations of n -dimensional Euclidean space that fix a given point (the origin).

  3. List of refrigerants - Wikipedia

    en.wikipedia.org/wiki/List_of_refrigerants

    For example, R-22 has one carbon atom, one hydrogen atom (2−1 = 1), two fluorine atoms, and one chlorine atom (4−2−1 = 1), so it is chlorodifluoromethane, while R-134 has two carbon atoms (2−1 = 1), two hydrogen atoms (3−1 = 2), four fluorine atoms, and no chlorine atoms (6−2−4 = 0), so it is one of the tetrafluoroethanes. This ...

  4. Presentation of a group - Wikipedia

    en.wikipedia.org/wiki/Presentation_of_a_group

    For example, the dihedral group D 8 of order sixteen can be generated by a rotation, r, of order 8; and a flip, f, of order 2; and certainly any element of D 8 is a product of r ' s and f ' s. However, we have, for example, rfr = f −1, r 7 = r −1, etc., so such products are not unique in D 8. Each such product equivalence can be expressed ...

  5. Linear group - Wikipedia

    en.wikipedia.org/wiki/Linear_group

    Basic examples are orthogonal, unitary and symplectic groups but it is possible to construct more using division algebras (for example the unit group of a quaternion algebra is a classical group). Note that the projective groups associated to these groups are also linear, though less obviously.

  6. Group representation - Wikipedia

    en.wikipedia.org/wiki/Group_representation

    This holds in particular for any representation of a finite group over the complex numbers, since the characteristic of the complex numbers is zero, which never divides the size of a group. In the example above, the first two representations given (ρ and σ) are both decomposable into two 1-dimensional subrepresentations (given by span{(1,0 ...

  7. SL2 (R) - Wikipedia

    en.wikipedia.org/wiki/SL2(R)

    SL(2, R) is the group of all linear transformations of R 2 that preserve oriented area. It is isomorphic to the symplectic group Sp(2, R) and the special unitary group SU(1, 1). It is also isomorphic to the group of unit-length coquaternions. The group SL ± (2, R) preserves unoriented area: it may reverse orientation.

  8. Carboxylic acid - Wikipedia

    en.wikipedia.org/wiki/Carboxylic_acid

    The general formula of a carboxylic acid is often written as R−COOH or R−CO 2 H, sometimes as R−C(O)OH with R referring to an organyl group (e.g., alkyl, alkenyl, aryl), or hydrogen, or other groups. Carboxylic acids occur widely. Important examples include the amino acids and fatty acids. Deprotonation of a carboxylic acid gives a ...

  9. Alcohol (chemistry) - Wikipedia

    en.wikipedia.org/wiki/Alcohol_(chemistry)

    The simplest example is tert-butanol (2-methylpropan-2-ol), for which each of R, R', and R" is CH 3. In these shorthands, R, R', and R" represent substituents , alkyl or other attached, generally organic groups.