隐函数定理:修订间差异
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== 参考来源 == |
== 参考来源 == |
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* {{en}}{{cite web|url=http://www.econ.iastate.edu/classes/econ500/hallam/documents/ImplicitFunction.pdf |title=The implicite function theorem|author= Arne Hallam|publisher=Iowa State University}} |
* {{en}}{{cite web|url=http://www.econ.iastate.edu/classes/econ500/hallam/documents/ImplicitFunction.pdf |title=The implicite function theorem|author= Arne Hallam|publisher=Iowa State University}} |
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*{{Cite book |
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| ref = harv |
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| last = Chiang |
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| first = Alpha C. |
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| title = Fundamental Methods of Mathematical Economics |
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| publisher = McGraw-Hill |
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| edition = 3rd |
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| year = 1984 |
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}} |
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*{{springer |
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| title = Implicit function (in algebraic geometry) |
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| id = i/i050320 |
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| last = Danilov |
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| first = V.I. |
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}}. |
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*{{Cite book |
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| ref = harv |
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| last = Edwards |
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| first = Charles Henry |
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| title = Advanced Calculus of Several Variables |
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| publisher = Dover Publications |
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| location = Mineola, New York |
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| year = 1994 |
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| origyear = 1973 |
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| isbn = 978-0-486-68336-2 |
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}} |
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*{{Cite book |
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| ref = harv |
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| first1 = K. |
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| last1 = Fritzsche |
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| first2 = H. |
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| last2 = Grauert |
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| year = 2002 |
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| url = https://books.google.com/books?id=jSeRz36zXIMC&lpg=PP1&dq=fritzsche%20grauert&hl=de&pg=PA34#v=onepage&q&f=false |
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| title = From Holomorphic Functions to Complex Manifolds |
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| publisher = Springer |
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}} |
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*{{Cite journal |
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| ref = harv |
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| first = K. |
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| last = Jittorntrum |
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| title = An Implicit Function Theorem |
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| journal = Journal of Optimization Theory and Applications |
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| volume = 25 |
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| issue = 4 |
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| year = 1978 |
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| doi = 10.1007/BF00933522 |
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}} |
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*{{springer |
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| title = Implicit function |
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| id = i/i050310 |
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| last = Kudryavtsev |
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| first = Lev Dmitrievich |
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}}. |
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*{{Cite journal |
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| ref = harv |
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| first = S. |
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| last = Kumagai |
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| title = An implicit function theorem: Comment |
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| journal = Journal of Optimization Theory and Applications |
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| volume = 31 |
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| issue = 2 |
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| year = 1980 |
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| doi = 10.1007/BF00934117 |
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}} |
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*{{Cite book |
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| ref = harv |
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| last = Lang |
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| first = Serge |
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| author-link=Serge Lang |
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| title = Fundamentals of Differential Geometry |
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| year = 1999 |
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| publisher = Springer |
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| location = New York |
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| series = Graduate Texts in Mathematics |
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| isbn = 978-0-387-98593-0 |
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}} |
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[[Category:多变量微积分]] |
[[Category:多变量微积分]] |
2016年12月26日 (一) 12:21的版本
在数学中,隐函数定理是一个描述关系以隐函数表示的某些变量之间是否存在显式关系的定理。隐函数定理说明,对于一个由关系表示的隐函数,如果它在某一点附近的微分满足某些条件,则在这点附近,可以表示成关于的函数:
这样就把隐函数关系变成了常见的函数关系。
例子
定义函数,那么方程的所有解的集合构成单位圆()。圆上的点是无法用统一的方法表示成的形式的,因为每个都有两个的值与之对应,即。
然而,局部地用来表示是可以的。给定圆上一点,如果,也就是说这点在圆的上半部分的话,在这一点附近可以写成关于的函数:。如果,附近的也可以写成关于的函数:。
但是,在点的附近,无法写成关于的函数,因为的每一个邻域中都包含了上半圆和下半圆的点,于是对于附近的每一个,都有两个的值与之对应。
定理的叙述:欧几里得空间的情况
设f : Rn+m → Rm为一个连续可微函数。这里Rn+m被看作是两个空间的直积:Rn×Rm,于是Rn+m中的一个元素写成 (x,y) = (x1, ..., xn, y1, ..., ym)的形式。
对于任意一点(a,b) = (a1, ..., an, b1, ..., bm)使得f(a, b) = 0,隐函数定理给出了能否在(a,b)附近定义一个y关于x的函数g,使得只要:f(x,y)=0,就有y = g( x )的充分条件。这样的函数g存在的话,严格来说,就是说存在a和b的邻域U和V,使得g的定义域是:g : U → V,并且g的函数图像满足:
隐函数定理说明,要使的这样的函数g存在,函数的雅可比矩阵一定要满足一定的性质。对于给定的一点 (a,b),的雅可比矩阵写作:
其中的矩阵是关于的偏微分,而是关于的偏微分。隐函数定理说明了:如果是一个可逆的矩阵的话,那么满足前面性质的、和函数就会存在。概括地写出来,就是:
一般情形
设、和是三个巴拿赫空间,而、分别是、上的两个开集。设函数:
是一个的函数(见光滑函数),其中,并且对于中的一点,满足:
- ,
那么有如下结论:
- 。
参见
参考来源
- (英文)Arne Hallam. The implicite function theorem (PDF). Iowa State University.
- Chiang, Alpha C. Fundamental Methods of Mathematical Economics 3rd. McGraw-Hill. 1984.
- Danilov, V.I., Implicit function (in algebraic geometry), Hazewinkel, Michiel (编), 数学百科全书, Springer, 2001, ISBN 978-1-55608-010-4.
- Edwards, Charles Henry. Advanced Calculus of Several Variables. Mineola, New York: Dover Publications. 1994 [1973]. ISBN 978-0-486-68336-2.
- Fritzsche, K.; Grauert, H. From Holomorphic Functions to Complex Manifolds. Springer. 2002.
- Jittorntrum, K. An Implicit Function Theorem. Journal of Optimization Theory and Applications. 1978, 25 (4). doi:10.1007/BF00933522.
- Kudryavtsev, Lev Dmitrievich, Implicit function, Hazewinkel, Michiel (编), 数学百科全书, Springer, 2001, ISBN 978-1-55608-010-4.
- Kumagai, S. An implicit function theorem: Comment. Journal of Optimization Theory and Applications. 1980, 31 (2). doi:10.1007/BF00934117.
- Lang, Serge. Fundamentals of Differential Geometry. Graduate Texts in Mathematics. New York: Springer. 1999. ISBN 978-0-387-98593-0.