Definisi limit (ε, δ): Perbedaan antara revisi
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{{Short description|Definisi matematis limit}}{{Under construction}}{{DISPLAYTITLE:(''ε'', ''δ'')-definisi limit}}
{{periksaterjemahan|en|(ε, δ)-definition of limit}}
[[Berkas:Límite 01.svg|thumb|right|Kapanpun suatu titik ''x'' is within ''δ'' unit ''c'', ''f''(''x'') berada dalam ε unit ''L'']]
Dalam [[kalkulus]], '''(''ε'', ''δ'')-definisi limit''' ("[[epsilon]]–[[delta (huruf)|delta]] definisi limit") adalah formalisasi dari pengertian [[Limit fungsi|limit]]. Konsep tersebut karena [[Augustin-Louis Cauchy]], yang tidak pernah memberi nilai (<math>\varepsilon,\delta</math>)
{{citation
|title=Siapa yang Memberi Anda Epsilon? Cauchy dan Origins of Rigorous Calculus
Baris 38 ⟶ 37:
|access-date = 2009-05-01
|df =
}}. Accessed 2009-05-01.</ref> Hal tersebut memberikan ketelitian pada gagasan informal berikut:
==Sejarah==
Meskipun orang Yunani memeriksa proses pembatasan, seperti [[metode Babilonia]], mereka mungkin tidak memiliki konsep yang mirip dengan modern limit.<ref>{{cite book|last1=Stillwell|first1=John|authorlink=John Stillwell|title=Matematika dan Sejarahnya|url=https://archive.org/details/mathematicsitshi0000stil|url-access=registration|date=1989|publisher=Springer-Verlag|location=New York|isbn=978-1-4899-0007-4|pages=[https://archive.org/details/mathematicsitshi0000stil/page/38 38–39]}}</ref> Ketentuan konsep limit muncul pada tahun 1600-an, ketika [[Pierre de Fermat]] berusaha menemukan [[
:<math>
\begin{align}
\text{
& = \frac{(x+E)^2-x^2}{E}\\
& = \frac{x^2+2xE+E^2-x^2}{E} \\
& = \frac{2xE+E^2}{E} = 2x+E = 2x
\end{align}
</math>
Kunci dari perhitungan di atas adalah sejak <math>E</math>
Masalah ini muncul kembali kemudian pada tahun
Additionally, Newton occasionally explained limits in terms similar to the epsilon–delta definition.<ref>{{citation|title=Newton and the Notion of Limit| first1=B.|last1=Pourciau|journal=Historia Mathematica|volume=28|issue=1| pages=18–30|year=2001|doi=10.1006/hmat.2000.2301 }}</ref> [[Gottfried Wilhelm Leibniz]] developed an infinitesimal of his own and tried to provide it with a rigorous footing, but it was still greeted with unease by some mathematicians and philosophers.<ref>{{cite book|last1=Buckley|first1=Benjamin Lee|title=The continuity debate : Dedekind, Cantor, du Bois-Reymond and Peirce on continuity and infinitesimals|date=2012|isbn=9780983700487|page=32}}</ref>▼
: Rasio terakhirnya ... sebenarnya bukan rasio kauntitas terakhirnya, tetapi limit ... yang mana ini dapat didekatkan lebih dekat bahwa perbedaannya lebih kecil dari suatu kuantitas yang diberikan...
[[Augustin-Louis Cauchy]] gave a definition of limit in terms of a more primitive notion he called a ''variable quantity''. He never gave an epsilon–delta definition of limit (Grabiner 1981). Some of Cauchy's proofs contain indications of the epsilon–delta method. Whether or not his foundational approach can be considered a harbinger of Weierstrass's is a subject of scholarly dispute. Grabiner feels that it is, while Schubring (2005) disagrees.{{dubious|date=December 2011}}<ref name="grabiner" /> Nakane concludes that Cauchy and Weierstrass gave the same name to different notions of limit.<ref>Nakane, Michiyo. Did Weierstrass's differential calculus have a limit-avoiding character? His definition of a limit in ''ε''−''δ'' style. BSHM Bull. 29 (2014), no. 1, 51–59.</ref>{{Unreliable source?|date=April 2015}}▼
▲
▲[[Augustin-Louis Cauchy]]
:<math>▼
Eventually, Weierstrass and Bolzano are credited with providing a rigorous footing for calculus, in the form of the modern <math>\varepsilon\text{–}\delta</math> definition of the limit.<ref name="grabiner" /><ref>{{citation|first=A.-L.|last=Cauchy|author-link=Augustin Louis Cauchy|title=Résumé des leçons données à l'école royale polytechnique sur le calcul infinitésimal|place=Paris|year=1823|url=http://math-doc.ujf-grenoble.fr/cgi-bin/oeitem?id=OE_CAUCHY_2_4_9_0|chapter=Septième Leçon - Valeurs de quelques expressions qui se présentent sous les formes indéterminées <math>\frac{\infty}{\infty}, \infty^0, \ldots</math> Relation qui existe entre le rapport aux différences finies et la fonction dérivée|chapter-url=http://gallica.bnf.fr/ark:/12148/bpt6k90196z/f45n5.capture|postscript=, [http://gallica.bnf.fr/ark:/12148/bpt6k90196z.image.f47 p. 44].|archive-url=https://www.webcitation.org/5gVUmywgY?url=http://math-doc.ujf-grenoble.fr/cgi-bin/oeitem?id=OE_CAUCHY_2_4_9_0|archive-date=2009-05-04|url-status=dead|access-date=2009-05-01|df=}}.</ref> The need for reference to an infinitesimal <math>E</math> was then removed,<ref>{{cite book|last1=Buckley|first1=Benjamin Lee|date=2012|title=The continuity debate : Dedekind, Cantor, du Bois-Reymond and Peirce on continuity and infinitesimals|isbn=9780983700487|page=33}}</ref> and Fermat's computation turned into the computation of the following limit:
▲: <math>
\lim_{h\to 0} \frac{f(x+h)-f(x)}{h}.
</math>
This is not to say that the limiting definition was free of problems as, although it removed the need for infinitesimals, it did require the construction of the [[
==Contoh yang bekerja==
===Contoh 1===
: <math>\lim_{x\to 0} x\sin{\left(\frac{1}{x}\right)} = 0
</math>.
Karena [[sinus]] dibatasi di atas <math>1</math> dan di bawahnya oleh
<math>
Baris 104 ⟶ 89:
</math>
Demikianlah, jika
===Contoh 2===
Pernyataan
: <math> \lim_{x\to a} x^2 = a^2</math>
: <math> |x^2-a^2| = |(x-a)(x+a)|=|x-a||x+a|
Jadi,
: <math> |x| - |a| \leq |x-a| < 1
Dengan demikian,
: <math> |x| < 1 + |a|
: <math> |x+a| \leq |x| + |a| < 2|a| + 1.</math>
:<math> |x-a| < \frac{\varepsilon}{2|a| +1}</math>
maka
:<math>|x^2-a^2| <\varepsilon
▲: <math> \delta = \min{\left(1,\frac{\varepsilon}{2|a| +1}\right)}.</math>
Jadi, jika <math> |x-a|<\delta</math>,
: <math>
Baris 150 ⟶ 134:
&< \frac{\varepsilon}{2|a| +1}(|x+a|)\\
&< \frac{\varepsilon}{2|a| +1}(2|a|+1)\\
&=\varepsilon
\end{align}
</math>
: <math> \lim_{x\to a} x^2 = a^2</math>
== Kekontinuan ==
== Perbandingan dengan definisi infinitesimal ==
== Keluarga definisi limit formal ==
Tidak ada definisi limit yang tunggal - adanya seluruh definisi keluarga. Ini dikarenakan kehadiran takhingga, dan konsep limit "dari sebelah kanan"" dan "dari sebelah kiri". Limit itu sendiri dapat menjadi sebuah nilai terhingga, <math>\infty</math>, atau <math>-\infty</math>. Nilai yang mendekati oleh <math>x</math> juga dapat menjadi nilai terhingga, <math>\infty</math>, atau <math>-\infty</math>, dan jika ini merupakan sebuah nilai terhingga, ini dapat mendekati dari kiri atau dari kanan. Biasanya, setiap kombinasinya diberikan definisi itu sendiri, seperti di bawah ini:{{Aligned table|'''Notation'''|179=<math>{\color{Red}-\infty}</math>|166=<math>{\color{Green}\exists M < 0, }</math>|167=<math>\forall x \in D,</math>|168=|169=<math>x</math>|170=<math>< {\color{Green}M }</math>|171=<math>\Rightarrow</math>|172=<math>{\color{Red}N} <</math>|173=<math>f(x)</math>|174=|175=|176=<math>\lim_{x \to -\infty} x^2 = \infty</math>|177=<math>\lim_{x \to {\color{Green}c}}</math>|178=<math>f(x) =</math>|180=<math>\iff</math>|164=<math>\iff</math>|181=<math>{\color{Red}\forall N < 0,}</math>|182=<math>{\color{Green}\exists \delta > 0,}</math>|183=<math>\forall x \in D,</math>|184=<math>{\color{Green}c-\delta} <</math>|185=<math>x</math>|186=<math>< {\color{Green}c+\delta}</math>|187=<math>\Rightarrow</math>|188=|189=<math>f(x)</math>|190=<math>< {\color{Red}N}</math>|191=|192=<math>\lim_{x \to 0} -|1/x| = -\infty</math>|193=<math>\lim_{x \to {\color{Green}c^+}}</math>|165=<math>{\color{Red}\forall N > 0,}</math>|163=<math>{\color{Red}\infty}</math>|195=<math>{\color{Red}-\infty}</math>|146=<math>f(x) =</math>|133=<math>{\color{Red}\forall N > 0,}</math>|134=<math>{\color{Green}\exists \delta > 0,}</math>|135=<math>\forall x \in D,</math>|136=<math>{\color{Green}c-\delta} <</math>|137=<math>x</math>|138=<math>< {\color{Green}c }</math>|139=<math>\Rightarrow</math>|140=<math>{\color{Red}N} <</math>|141=<math>f(x)</math>|142=|143=|144=<math>\lim_{x \to 0^-} -1/x = \infty</math>|145=<math>\lim_{x \to {\color{Green}\infty}}</math>|147=<math>{\color{Red}\infty}</math>|162=<math>f(x) =</math>|148=<math>\iff</math>|149=<math>{\color{Red}\forall N > 0,}</math>|150=<math>{\color{Green}\exists M > 0, }</math>|151=<math>\forall x \in D,</math>|152=<math>{\color{Green}M } <</math>|153=<math>x</math>|154=|155=<math>\Rightarrow</math>|156=<math>{\color{Red}N} <</math>|157=<math>f(x)</math>|158=|159=|160=<math>\lim_{x \to \infty} e^x = \infty</math>|161=<math>\lim_{x \to {\color{Green}-\infty}}</math>|194=<math>f(x) =</math>|196=<math>\iff</math>|131=<math>{\color{Red}\infty}</math>|244=<math>\iff</math>|231=<math>\forall x \in D,</math>|232=<math>{\color{Green}M } <</math>|233=<math>x</math>|234=|235=<math>\Rightarrow</math>|236=|237=<math>f(x)</math>|238=<math>< {\color{Red}N}</math>|239=|240=<math>\lim_{x \to \infty} -x = -\infty</math>|241=<math>\lim_{x \to {\color{Green}-\infty}}</math>|242=<math>f(x) =</math>|243=<math>{\color{Red}-\infty}</math>|245=<math>{\color{Red}\forall N < 0,}</math>|229=<math>{\color{Red}\forall N < 0,}</math>|246=<math>{\color{Green}\exists M < 0, }</math>|247=<math>\forall x \in D,</math>|248=|249=<math>x</math>|250=<math>< {\color{Green}M }</math>|251=<math>\Rightarrow</math>|252=|253=<math>f(x)</math>|254=<math>< {\color{Red}N}</math>|255=|256=<math>\lim_{x \to -\infty} x^3 = -\infty</math>|cols=16|col8align=right|230=<math>{\color{Green}\exists M > 0, }</math>|228=<math>\iff</math>|197=<math>{\color{Red}\forall N < 0,}</math>|211=<math>{\color{Red}-\infty}</math>|198=<math>{\color{Green}\exists \delta > 0,}</math>|199=<math>\forall x \in D,</math>|200=<math>{\color{Green}c } <</math>|201=<math>x</math>|202=<math>< {\color{Green}c+\delta}</math>|203=<math>\Rightarrow</math>|204=|205=<math>f(x)</math>|206=<math>< {\color{Red}N}</math>|207=|208=<math>\lim_{x \to 0^+} log(x) = -\infty</math>|209=<math>\lim_{x \to {\color{Green}c^-}}</math>|210=<math>f(x) =</math>|212=<math>\iff</math>|227=<math>{\color{Red}-\infty}</math>|213=<math>{\color{Red}\forall N < 0,}</math>|214=<math>{\color{Green}\exists \delta > 0,}</math>|215=<math>\forall x \in D,</math>|216=<math>{\color{Green}c-\delta} <</math>|217=<math>x</math>|218=<math>< {\color{Green}c }</math>|219=<math>\Rightarrow</math>|220=|221=<math>f(x)</math>|222=<math>< {\color{Red}N}</math>|223=|224=<math>\lim_{x \to 0^-} 1/x = -\infty</math>|225=<math>\lim_{x \to {\color{Green}\infty}}</math>|226=<math>f(x) =</math>|132=<math>\iff</math>|130=<math>f(x) =</math>||49=<math>\lim_{x \to {\color{Green}c^-}}</math>|36=<math>\iff</math>|37=<math>{\color{Red}\forall\varepsilon > 0,}</math>|38=<math>{\color{Green}\exists \delta > 0,}</math>|39=<math>\forall x \in D,</math>|40=<math>{\color{Green}c } <</math>|41=<math>x</math>|42=<math>< {\color{Green}c+\delta}</math>|43=<math>\Rightarrow</math>|44=<math>{\color{Red}L-\varepsilon} <</math>|45=<math>f(x)</math>|46=<math>< {\color{Red}L+\varepsilon}</math>|47=|48=<math>\lim_{x \to 0^+} x^2 + sgn(x) = 1</math>|50=<math>f(x) =</math>|34=<math>f(x) =</math>|51=<math>{\color{Red}L}</math>|52=<math>\iff</math>|53=<math>{\color{Red}\forall\varepsilon > 0,}</math>|54=<math>{\color{Green}\exists \delta > 0,}</math>|55=<math>\forall x \in D,</math>|56=<math>{\color{Green}c-\delta} <</math>|57=<math>x</math>|58=<math>< {\color{Green}c }</math>|59=<math>\Rightarrow</math>|60=<math>{\color{Red}L-\varepsilon} <</math>|61=<math>f(x)</math>|62=<math>< {\color{Red}L+\varepsilon}</math>|63=|35=<math>{\color{Red}L}</math>|33=<math>\lim_{x \to {\color{Green}c^+}}</math>|65=<math>\lim_{x \to {\color{Green}\infty}}</math>|16='''Example'''|||'''Def.'''|||||||||||17=<math>\lim_{x \to {\color{Green}c}}</math>|32=<math>\lim_{x \to 0} sin(x) = 0</math>|18=<math>f(x) =</math>|19=<math>{\color{Red}L}</math>|20=<math>\iff</math>|21=<math>{\color{Red}\forall\varepsilon > 0,}</math>|22=<math>{\color{Green}\exists \delta > 0,}</math>|23=<math>\forall x \in D,</math>|24=<math>{\color{Green}c-\delta} <</math>|25=<math>x</math>|26=<math>< {\color{Green}c+\delta}</math>|27=<math>\Rightarrow</math>|28=<math>{\color{Red}L-\varepsilon} <</math>|29=<math>f(x)</math>|30=<math>< {\color{Red}L+\varepsilon}</math>|31=|64=<math>\lim_{x \to 0^-} x^2 + sgn(x) = -1</math>|66=<math>f(x) =</math>|129=<math>\lim_{x \to {\color{Green}c^-}}</math>|114=<math>f(x) =</math>|101=<math>{\color{Red}\forall N > 0,}</math>|102=<math>{\color{Green}\exists \delta > 0,}</math>|103=<math>\forall x \in D,</math>|104=<math>{\color{Green}c-\delta} <</math>|105=<math>x</math>|106=<math>< {\color{Green}c+\delta}</math>|107=<math>\Rightarrow</math>|108=<math>{\color{Red}N} <</math>|109=<math>f(x)</math>|110=|111=|112=<math>\lim_{x \to 0} |1/x| = \infty</math>|113=<math>\lim_{x \to {\color{Green}c^+}}</math>|115=<math>{\color{Red}\infty}</math>|99=<math>{\color{Red}\infty}</math>|116=<math>\iff</math>|117=<math>{\color{Red}\forall N > 0,}</math>|118=<math>{\color{Green}\exists \delta > 0,}</math>|119=<math>\forall x \in D,</math>|120=<math>{\color{Green}c } <</math>|121=<math>x</math>|122=<math>< {\color{Green}c+\delta}</math>|123=<math>\Rightarrow</math>|124=<math>{\color{Red}N} <</math>|125=<math>f(x)</math>|126=|127=|128=<math>\lim_{x \to 0^+} 1/x = \infty</math>|100=<math>\iff</math>|98=<math>f(x) =</math>|67=<math>{\color{Red}L}</math>|81=<math>\lim_{x \to {\color{Green}-\infty}}</math>|68=<math>\iff</math>|69=<math>{\color{Red}\forall\varepsilon > 0,}</math>|70=<math>{\color{Green}\exists M > 0, }</math>|71=<math>\forall x \in D,</math>|72=<math>{\color{Green}M } <</math>|73=<math>x</math>|74=|75=<math>\Rightarrow</math>|76=<math>{\color{Red}L-\varepsilon} <</math>|77=<math>f(x)</math>|78=<math>< {\color{Red}L+\varepsilon}</math>|79=|80=<math>\lim_{x \to \infty} 1/x = 0</math>|82=<math>f(x) =</math>|97=<math>\lim_{x \to {\color{Green}c}}</math>|83=<math>{\color{Red}L}</math>|84=<math>\iff</math>|85=<math>{\color{Red}\forall\varepsilon > 0,}</math>|86=<math>{\color{Green}\exists M < 0, }</math>|87=<math>\forall x \in D,</math>|88=|89=<math>x</math>|90=<math>< {\color{Green}M }</math>|91=<math>\Rightarrow</math>|92=<math>{\color{Red}L-\varepsilon} <</math>|93=<math>f(x)</math>|94=<math>< {\color{Red}L+\varepsilon}</math>|95=|96=<math>\lim_{x \to -\infty} e^x = 0</math>|col12align=right}}
== Referensi ==
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