matlab中编写开平方根怎么编写啊？比如a=c*d+e;k=g*d+f*s;求开平方eqrt（a^2+k^2）_百度知道
matlab中编写开平方根怎么编写啊？比如a=c*d+e;k=g*d+f*s;求开平方eqrt（a^2+k^2）
我有更好的答案
syms c d e f g sa=c*d+e;k=g*d+f*s;yy=sqrt(a^2+k^2)
采纳率：88%
来自团队：
sqrt,需要double型
就是全是字母需要把几个公式化成一个公式，这个公式的形式就是前面三个公式的平方和开方。就是不知道字母怎么定义
不太懂你的意思，你把程序贴出来我看看
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This article's
may be too long for the length of the article. Please help by moving some material from it into the body of the article. Please read the
to ensure the section will still be inclusive of all essential details. Please discuss this issue on the article's . (May 2016)
Infinitesimals (ε) and infinites (ω) on the hyperreal number line (ε = 1/ω)
In , infinitesimals are things so small that there is no way to measure them. The insight with exploiting infinitesimals was that entities could still retain certain specific properties, such as
or , even though these entities were quantitatively small. The word infinitesimal comes from a 17th-century
coinage infinitesimus, which originally referred to the "" item in a sequence. Infinitesimals are a basic ingredient in the procedures of infinitesimal
as developed by Leibniz, including the
and the . In common speech, an infinitesimal object is an object that is smaller than any feasible measurement, but not zero in size—or, so small that it cannot be distinguished from zero by any available means. Hence, when used as an adjective, "infinitesimal" means "extremely small". To give it a meaning, it usually must be compared to another infinitesimal object in the same context (as in a ). Infinitely many infinitesimals are summed to produce an .
The concept of infinitesimals was originally introduced around 1670 by either
used what eventually came to be known as the
in his work
to find areas of regions and volumes of solids. In his formal published treatises, Archimedes solved the same problem using the . The 15th century saw the work of , further developed in the 17th century by , in particular calculation of area of a circle by representing the latter as an infinite-sided polygon. 's work on decimal representation of all numbers in the 16th century prepared the ground for the real continuum. 's method of indivisibles led to an extension of the results of the classical authors. The method of indivisibles related to geometrical figures as being composed of entities of
1. 's infinitesimals differed from indivisibles in that he would decompose geometrical figures into infinitely thin building blocks of the same dimension as the figure, preparing the ground for general methods of the integral calculus. He exploited an infinitesimal denoted
in area calculations.
The use of infinitesimals by Leibniz relied upon heuristic principles, such as the law of continuity: what succeeds for the finite numbers succeeds also for the infinite nu and the transcendental law of homogeneity that specifies procedures for replacing expressions involving inassignable quantities, by expressions involving only assignable ones. The 18th century saw routine use of infinitesimals by mathematicians such as
exploited infinitesimals both in defining
in his , and in defining an early form of a . As Cantor and Dedekind were developing more abstract versions of Stevin's continuum,
wrote a series of papers on infinitesimal-enriched continua based on growth rates of functions. Du Bois-Reymond's work inspired both
and . Borel explicitly linked du Bois-Reymond's work to Cauchy's work on rates of growth of infinitesimals. Skolem developed the first non-standard models of arithmetic in 1934. A mathematical implementation of both the law of continuity and infinitesimals was achieved by
in 1961, who developed
based on earlier work by
in 1948 and
in 1955. The
implement an infinitesimal-enriched continuum and the
implements Leibniz's law of continuity. The
implements Fermat's .
wrote in 1990:
Nowadays, when teaching analysis, it is not very popular to talk about infinitesimal quantities. Consequently present-day students are not fully in command of this language. Nevertheless, it is still necessary to have command of it.
The notion of infinitely small quantities was discussed by the . The
mathematician
(c.287 BC–c.212 BC), in , was the first to propose a logically rigorous definition of infinitesimals. His
defines a number x as infinite if it satisfies the conditions |x|&1, |x|&1+1, |x|&1+1+1, ..., and infinitesimal if x≠0 and a similar set of conditions holds for x and the reciprocals of the positive integers. A number system is said to be Archimedean if it contains no infinite or infinitesimal members.
The English mathematician
introduced the expression 1/∞ in his 1655 book Treatise on the Conic Sections. The symbol, which denotes the reciprocal, or inverse, of , is the symbolic representation of the mathematical concept of an infinitesimal. In his Treatise on the Conic Sections Wallis also discusses the concept of a relationship between the symbolic representation of infinitesimal 1/∞ that he introduced and the concept of infinity for which he introduced the symbol ∞. The concept suggests a
of adding an infinite number of
of infinitesimal width to form a finite area. This concept was the predecessor to the modern method of integration used in . The conceptual origins of the concept of the infinitesimal 1/∞ can be traced as far back as the Greek philosopher , whose
was the first mathematical concept to consider the relationship between a finite interval and an interval approaching that of an infinitesimal-sized interval.
Infinitesimals were the subject of political and religious controversies in 17th century Europe, including a ban on infinitesimals issued by clerics in Rome in 1632.
Prior to the invention of calculus mathematicians were able to calculate tangent lines using 's method of
and ' . There is debate among scholars as to whether the method was infinitesimal or algebraic in nature. When
invented the , they made use of infinitesimals, Newton's
and Leibniz' . The use of infinitesimals was attacked as incorrect by
in his work . Mathematicians, scientists, and engineers continued to use infinitesimals to produce correct results. In the second half of the nineteenth century, the calculus was reformulated by , , , , , and others using the
and . While the followers of Cantor, Dedekind, and Weierstrass sought to rid analysis of infinitesimals, and their philosophical allies like
declared that infinitesimals are pseudoconcepts,
sought to develop a working logic of infinitesimals. The mathematical study of systems containing infinitesimals continued through the work of , , , and others, throughout the late nineteenth and the twentieth centuries, as documented by
(2006). In the 20th century, it was found that infinitesimals could serve as a basis for c see .
In extending the real numbers to include infinite and infinitesimal quantities, one typically wishes to be as conservative as possible by not changing any of their elementary properties. This guarantees that as many familiar results as possible are still available. Typically elementary means that there is no
over , but only over elements. This limitation allows statements of the form "for any number x..." For example, the axiom that states "for any number x, x + 0 = x" would still apply. The same is true for quantification over several numbers, e.g., "for any numbers x and y, xy = yx." However, statements of the form "for any set S of numbers ..." may not carry over. Logic with this limitation on quantification is referred to as .
The resulting extended number system cannot agree with the reals on all properties that can be expressed by quantification over sets, because the goal is to construct a non-Archimedean system, and the Archimedean principle can be expressed by quantification over sets. One can conservatively extend any theory including reals, including set theory, to include infinitesimals, just by adding a countably infinite list of axioms that assert that a number is smaller than 1/2, 1/3, 1/4 and so on. Similarly, the
property cannot be expected to carry over, because the reals are the unique complete ordered field up to isomorphism.
We can distinguish three levels at which a nonarchimedean number system could have first-order properties compatible with those of the reals:
obeys all the usual axioms of the real number system that can be stated in first-order logic. For example, the
axiom x + y = y + x holds.
has all the first-order properties of the real number system, regardless of whether they are usually taken as axiomatic, for statements involving the basic ordered-field relations +, ×, and ≤. This is a stronger condition than obeying the ordered-field axioms. More specifically, one includes additional first-order properties, such as the existence of a root for every odd-degree polynomial. For example, every number must have a .
The system could have all the first-order properties of the real number system for statements involving any relations (regardless of whether those relations can be expressed using +, ×, and ≤). For example, there would have to be a
function that is well defined the same is true for every real function.
Systems in category 1, at the weak end of the spectrum, are relatively easy to construct, but do not allow a full treatment of classical analysis using infinitesimals in the spirit of Newton and Leibniz. For example, the
are defined in terms of infinite limiting processes, and therefore there is typically no way to define them in first-order logic. Increasing the analytic strength of the system by passing to categories 2 and 3, we find that the flavor of the treatment tends to become less constructive, and it becomes more difficult to say anything concrete about the hierarchical structure of infinities and infinitesimals.
An example from category 1 above is the field of
with a finite number of negative-power terms. For example, the Laurent series consisting only of the constant term 1 is identified with the real number 1, and the series with only the linear term x is thought of as the simplest infinitesimal, from which the other infinitesimals are constructed. Dictionary ordering is used, which is equivalent to considering higher powers of x as negligible compared to lower powers.
refers to this system as the super-reals, not to be confused with the
system of Dales and Woodin. Since a Taylor series evaluated with a Laurent series as its argument is still a Laurent series, the system can be used to do calculus on transcendental functions if they are analytic. These infinitesimals have different first-order properties than the reals because, for example, the basic infinitesimal x does not have a square root.
is similar to the Laurent series, but is algebraically closed. For example, the basic infinitesimal x has a square root. This field is rich enough to allow a significant amount of analysis to be done, but its elements can still be represented on a computer in the same sense that real numbers can be represented in floating point.
The field of
is larger than the Levi-Civita field. An example of a transseries is:
{\displaystyle e^{\sqrt {\ln \ln x}}+\ln \ln x+\sum _{j=0}^{\infty }e^{x}x^{-j},}
where for purposes of ordering x is considered infinite.
fall into category 2. They are a system designed to be as rich as possible in different sizes of numbers, but not necessarily for convenience in doing analysis. Certain transcendental functions can be carried over to the surreals, including logarithms and exponentials, but most, e.g., the sine function, cannot[]. The existence of any particular surreal number, even one that has a direct counterpart in the reals, is not known a priori, and must be proved.[]
The most widespread technique for handling infinitesimals is the hyperreals, developed by
in the 1960s. They fall into category 3 above, having been designed that way so all of classical analysis can be carried over from the reals. This property of being able to carry over all relations in a natural way is known as the , proved by
in 1955. For example, the transcendental function sin has a natural counterpart *sin that takes a hyperreal input and gives a hyperreal output, and similarly the set of natural numbers
{\displaystyle \mathbb {N} }
has a natural counterpart
{\displaystyle ^{*}\mathbb {N} }
, which contains both finite and infinite integers. A proposition such as
{\displaystyle \forall n\in \mathbb {N} ,\sin n\pi =0}
carries over to the hyperreals as
{\displaystyle \forall n\in {}^{*}\mathbb {N} ,{}^{*}\!\!\sin n\pi =0}
system of Dales and Woodin is a generalization of the hyperreals. It is different from the super-real system defined by .
extend the reals by adjoining one infinitesimal, the new element ε with the property ε2 = 0 (that is, ε is ). Every dual number has the form z = a + bε with a and b being uniquely determined real numbers.
One application of dual numbers is . This application can be generalized to polynomials in n variables, using the
of an n-dimensional vector space.
have roots in . This approach departs from the classical logic used in conventional mathematics by denying the general applicability of the
– i.e., not (a ≠ b) does not have to mean a = b. A nilsquare or
infinitesimal can then be defined. This is a number x where x2 = 0 is true, but x = 0 need not be true at the same time. Since the background logic is , it is not immediately clear how to classify this system with regard to classes 1, 2, and 3. Intuitionistic analogues of these classes would have to be developed first.
used an infinitesimal
{\displaystyle \alpha }
to write down a unit impulse, infinitely tall and narrow Dirac-type delta function
{\displaystyle \delta _{\alpha }}
satisfying
{\displaystyle \int F(x)\delta _{\alpha }(x)=F(0)}
in a number of articles in 1827, see Laugwitz (1989). Cauchy defined an infinitesimal in 1821 (Cours d'Analyse) in terms of a sequence tending to zero. Namely, such a null sequence becomes an infinitesimal in Cauchy's and 's terminology.
Modern set-theoretic approaches allow one to define infinitesimals via the
construction, where a null sequence becomes an infinitesimal in the sense of an equivalence class modulo a relation defined in terms of a suitable . The article by Yamashita (2007) contains a bibliography on modern
in the context of an infinitesimal-enriched continuum provided by the .
The method of constructing infinitesimals of the kind used in nonstandard analysis depends on the
and which collection of
are used. We consider here systems where infinitesimals can be shown to exist.
proved the . This theorem is fundamental for the existence of infinitesimals as it proves that it is possible to formalise them. A consequence of this theorem is that if there is a number system in which it is true that for any positive integer n there is a positive number x such that 0 & x & 1/n, then there exists an extension of that number system in which it is true that there exists a positive number x such that for any positive integer n we have 0 & x & 1/n. The possibility to switch "for any" and "there exists" is crucial. The first statement is true in the real numbers as given in
 : for any positive integer n it is possible to find a real number between 1/n and zero, but this real number depends on n. Here, one chooses n first, then one finds the corresponding x. In the second expression, the statement says that there is an x (at least one), chosen first, which is between 0 and 1/n for any n. In this case x is infinitesimal. This is not true in the real numbers (R) given by ZFC. Nonetheless, the theorem proves that there is a model (a number system) in which this is true. The question is: what is this model? What are its properties? Is there only one such model?
There are in fact many ways to construct such a
set of numbers, but fundamentally, there are two different approaches:
1) Extend the number system so that it contains more numbers than the real numbers.
2) Extend the axioms (or extend the language) so that the distinction between the infinitesimals and non-infinitesimals can be made in the real numbers themselves.
provided an answer following the first approach. The extended set is called the
and contains numbers less in absolute value than any positive real number. The method may be considered relatively complex but it does prove that infinitesimals exist in the universe of ZFC set theory. The real numbers are called standard numbers and the new non-real hyperreals are called .
provided an answer following the second approach. The extended axioms are IST, which stands either for
or for the initials of the three extra axioms: Idealization, Standardization, Transfer. In this system we consider that the language is extended in such a way that we can express facts about infinitesimals. The real numbers are either standard or nonstandard. An infinitesimal is a nonstandard real number that is less, in absolute value, than any positive standard real number.
In 2006 Karel Hrbacek developed an extension of Nelson's approach in which the real numbers are stratified in (infinitely) i.e., in the coarsest level there are no infinitesimals nor unlimited numbers. Infinitesimals are in a finer level and there are also infinitesimals with respect to this new level and so on.
Calculus textbooks based on infinitesimals include the classic
(bearing the motto "What one fool can do another can") and the German text Mathematik fur Mittlere Technische Fachschulen der Maschinenindustrie by R Neuendorff. Pioneering works based on 's infinitesimals include texts by
(dating from 1972) and
(). Students easily relate to the intuitive notion of an infinitesimal difference 1-"", where "0.999..." differs from its standard meaning as the real number 1, and is reinterpreted as an infinite terminating extended decimal that is strictly less than 1.
Another elementary calculus text that uses the theory of infinitesimals as developed by Robinson is Infinitesimal Calculus by Henle and Kleinberg, originally published in 1979. The authors introduce the language of first order logic, and demonstrate the construction of a first order model of the hyperreal numbers. The text provides an introduction to the basics of integral and differential calculus in one dimension, including sequences and series of functions. In an Appendix, they also treat the extension of their model to the hyperhyperreals, and demonstrate some applications for the extended model.
In a related but somewhat different sense, which evolved from the original definition of "infinitesimal" as an infinitely small quantity, the term has also been used to refer to a function tending to zero. More precisely, Loomis and Sternberg's Advanced Calculus defines the function class of infinitesimals,
{\displaystyle {\mathfrak {I}}}
, as a subset of functions
{\displaystyle f:V\to W}
between normed vector spaces by
{\displaystyle {\mathfrak {I}}(V,W)=\{f:V\to W\ |\ f(0)=0,(\forall \epsilon &0)(\exists \delta &0)\ \backepsilon \ ||\xi ||&\delta \implies ||f(\xi )||&\epsilon \}}
as well as two related classes
{\displaystyle {\mathfrak {O}},{\mathfrak {o}}}
{\displaystyle {\mathfrak {O}}(V,W)=\{f:V\to W\ |\ f(0)=0,\ (\exists r&0,c&0)\ \backepsilon \ ||\xi ||&r\implies ||f(\xi )||\leq c||\xi ||\}}
{\displaystyle {\mathfrak {o}}(V,W)=\{f:V\to W\ |\ f(0)=0,\ \lim _{||\xi ||\to 0}||f(\xi )||/||\xi ||=0\}}
The set inclusions
{\displaystyle {\mathfrak {o}}(V,W)\subsetneq {\mathfrak {O}}(V,W)\subsetneq {\mathfrak {I}}(V,W)}
generally hold. That the inclusions are proper is demonstrated by the real-valued functions of a real variable
{\displaystyle f:x\mapsto |x|^{1/2}}
{\displaystyle g:x\mapsto x}
{\displaystyle h:x\mapsto x^{2}}
{\displaystyle f,g,h\in {\mathfrak {I}}(\mathbb {R} ,\mathbb {R} ),\ g,h\in {\mathfrak {O}}(\mathbb {R} ,\mathbb {R} ),\ h\in {\mathfrak {o}}(\mathbb {R} ,\mathbb {R} )}
{\displaystyle f,g\notin {\mathfrak {o}}(\mathbb {R} ,\mathbb {R} )}
{\displaystyle f\notin {\mathfrak {O}}(\mathbb {R} ,\mathbb {R} )}
As an application of these definitions, a mapping
{\displaystyle F:V\to W}
between normed vector spaces is defined to be differentiable at
{\displaystyle \alpha \in V}
if there is a
{\displaystyle T\in \mathrm {Hom} (V,W)}
[i.e, a bounded linear map
{\displaystyle V\to W}
] such that
{\displaystyle [F(\alpha +\xi )-F(\alpha )]-T(\xi )\in {\mathfrak {o}}(V,W)}
in a neighborhood of
{\displaystyle \alpha }
. If such a map exists, this map is called the differential and is denoted by
{\displaystyle dF_{\alpha }}
, coinciding with the traditional notation for the classical (though logically flawed) notion of a differential as an infinitely small "piece" of F. This definition represents a generalization of the usual definition of differentiability for vector-valued functions of (open subsets of) Euclidean spaces.
{\displaystyle (\Omega ,{\mathcal {F}},\mathbb {P} )}
{\displaystyle n\in \mathbb {N} }
. An array
{\displaystyle \{X_{n,k}:\Omega \to \mathbb {R} \mid 1\leq k\leq k_{n}\}}
is called infinitesimal if for every
{\displaystyle \epsilon &0}
, we have:
 as 
{\displaystyle \max _{1\leq k\leq k_{n}}\mathbb {P} \{\omega \in \Omega \mid \vert X_{n,k}(\omega )\vert \geq \epsilon \}\to 0{\text{ as }}n\to \infty }
The notion of infinitesimal array is essential in some central limit theorems and it is easily seen by monotonicity of the expectation operator that any array satisfying
is infinitesimal, thus playing an important role in
(a generalization of the ).
*; Sherry, David (2012), "Leibniz's Infinitesimals: Their Fictionality, Their Modern Implementations, and Their Foes from Berkeley to Russell and Beyond", , : , :
Netz, R Saito, K Tchernetska, Natalie: A new reading of Method Proposition 14: preliminary evidence from the Archimedes palimpsest. I. SCIAMVS 2 (2001), 9–29.
Arnol?d, V. I. Huygens and Barrow, Newton and Hooke. Pioneers in mathematical analysis and catastrophe theory from evolvents to quasicrystals. Translated from the Russian by Eric J. F. Primrose. Birkh?user Verlag, Basel, 1990. p. 27
Archimedes, The Method of Mechanical Theorems; see
(2014). Infinitesimal: How a Dangerous Mathematical Theory Shaped the Modern World. Scientific American / Farrar, Straus and Giroux.  .
George Berkeley, The A or a discourse addressed to an infidel mathematician
; . Infinitesimals as an issue of neo-Kantian philosophy of science. : The Journal of the International Society for the History of Philosophy of Science 3 (2013), no. 2, 236–280. :.  . :.
. Jonhoyle.com. Archived from
Khodr Shamseddine, "Analysis on the Levi-Civia Field: A Brief Overview," []
G. A. Edgar, "Transseries for Beginners,"
Available online at
R Neuendorff (1912) Lehrbuch der Mathematik fur Mittlere Technische Fachschulen der Maschinenindustrie, Verlag Julius Springer, Berlin.
Ely, Robert (2010). "Nonstandard student conceptions about infinitesimals". . 41 (2): 117–146.  .
(PDF). Archived from
(PDF) on .
Henle, J Kleinberg, Eugene. Infinitesimal Calculus. The MIT Press, rereleased by Dover.
Loomis, Lynn H Sternberg, Shlomo (2014). . Hackensack, N.J.: World Scientific. pp. 138–142.  .
This notation is not to be confused with the many other distinct usages of d in calculus that are all loosely related to the classical notion of the differential as "taking an infinitesimally small piece of something": (1) in the expression
{\displaystyle \int f(x)\,d\alpha (x)}
{\displaystyle d\alpha (x)}
indicates Riemann-Stieltjes integration with respect to the integrator function
{\displaystyle \alpha }
; (2) in the expression
{\displaystyle \int f\,d\mu }
{\displaystyle d\mu }
symbolizes Lebesgue integration with respect to a measure
{\displaystyle \mu }
; (3) in the expression
{\displaystyle \int _{\mathbf {R} ^{n}}f\;dV}
, dV indicates integration wi (4) in the expression
{\displaystyle dx^{i_{1}}\wedge \cdots \wedge dx^{i_{n}}}
, the letter d represents the exterior derivative operator, and so on....
*Barczyk, A Janssen, A Pauly, Markus (2011). "The Asymptotics of L-statistics for non-i.i.d. variables with heavy tails". . 31 (2): 285–299.
B. Crowell, "Calculus" (2003)
Ehrlich, P. (2006) The rise of non-Archimedean mathematics and the roots of a misconception. I. The emergence of non-Archimedean systems of magnitudes. Arch. Hist. Exact Sci. 60, no. 1, 1–121.
. "Barrow, Wallis, and the remaking of seventeenth century indivisibles". Centaurus 39 (1997), no. 1, 67–92.
J. Keisler, "Elementary Calculus" (2000) University of Wisconsin
K. Stroyan "Foundations of Infinitesimal Calculus" (1993)
Introduction to the theory of infinitesimals. Pure and Applied Mathematics, No. 72. Academic Press [Harcourt Brace Jovanovich, Publishers], New York-London, 1976.
(1998) "Lectures on the hyperreals" Springer.
et al. "Nonstandard Methods and Applications in Mathematics" (2007) Lecture Notes in Logic 25, Association for Symbolic Logic.
"The Strength of Nonstandard Analysis" (2007) Springer.
(1989). "Definite values of infinite sums: aspects of the foundations of infinitesimal analysis around 1820". . 39 (3): 195–245. :.
Yamashita, H.: Comment on: "Pointwise analysis of scalar Fields: a nonstandard approach" [J. Math. Phys. 47 (2006), no. 9,
pp.]. J. Math. Phys. 48 (2007), no. 8,
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