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  2. Closed-form expression - Wikipedia

    en.wikipedia.org/wiki/Closed-form_expression

    The quadratic formula =. is a closed form of the solutions to the general quadratic equation + + =. More generally, in the context of polynomial equations, a closed form of a solution is a solution in radicals; that is, a closed-form expression for which the allowed functions are only n th-roots and field operations (+,,, /).

  3. Open formula - Wikipedia

    en.wikipedia.org/wiki/Open_formula

    An open formula is a formula that contains at least one free variable. [citation needed] An open formula does not have a truth value assigned to it, in contrast with a closed formula which constitutes a proposition and thus can have a truth value like true or false. An open formula can be transformed into a closed formula by applying a ...

  4. Sentence (mathematical logic) - Wikipedia

    en.wikipedia.org/wiki/Sentence_(mathematical_logic)

    In mathematical logic, a sentence (or closed formula) [1] of a predicate logic is a Boolean-valued well-formed formula with no free variables. A sentence can be viewed as expressing a proposition , something that must be true or false.

  5. Closed and exact differential forms - Wikipedia

    en.wikipedia.org/wiki/Closed_and_exact...

    In mathematics, especially vector calculus and differential topology, a closed form is a differential form α whose exterior derivative is zero (dα = 0), and an exact form is a differential form, α, that is the exterior derivative of another differential form β. Thus, an exact form is in the image of d, and a closed form is in the kernel of d.

  6. List of nonlinear ordinary differential equations - Wikipedia

    en.wikipedia.org/wiki/List_of_nonlinear_ordinary...

    A differential equation which may be solved with Bessel functions [13] Jacobi equation: 1 = + + + + + + + + Special case of the Darboux equation, integrable in closed form [14] Loewner differential equation: 1

  7. Differential equation - Wikipedia

    en.wikipedia.org/wiki/Differential_equation

    Differential equations play an important role in modeling virtually every physical, technical, or biological process, from celestial motion, to bridge design, to interactions between neurons. Differential equations such as those used to solve real-life problems may not necessarily be directly solvable, i.e. do not have closed form solutions

  8. Algebraically closed field - Wikipedia

    en.wikipedia.org/wiki/Algebraically_closed_field

    As an example, the field of real numbers is not algebraically closed, because the polynomial equation + = has no solution in real numbers, even though all its coefficients (1 and 0) are real. The same argument proves that no subfield of the real field is algebraically closed; in particular, the field of rational numbers is not algebraically closed.

  9. Integrability conditions for differential systems - Wikipedia

    en.wikipedia.org/wiki/Integrability_conditions...

    By the Poincaré lemma, the θ i locally will have the form dx i for some functions x i on the manifold, and thus provide an isometry of an open subset of M with an open subset of R n. Such a manifold is called locally flat. This problem reduces to a question on the coframe bundle of M. Suppose we had such a closed coframe