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19 (* $Id: Derivative.v,v 1.7 2004/04/23 10:00:58 lcf Exp $ *)
21 include "ftc/Continuity.ma".
29 We will now proceed toward the development of differential calculus.
30 To begin with, the main notion is that of derivative.
32 At this stage we will not define a notion of differentiable function,
33 mainly because the natural definition (that of being a function which
34 has some derivative) poses some technical problems; thus, we will
35 postpone that part of our work to a subsequent stage.
37 Derivative is a binary relation in the type of partial functions,
38 dependent (once again) on a compact interval with distinct
39 endpoints#. #%\footnote{%As before, we do not define pointwise
40 differentiability, mainly for coherence reasons. See Bishop [1967]
41 for a discussion on the relative little interest of that concept.%}.%
42 The reason for requiring the endpoints to be apart is mainly to be
43 able to derive the usual properties of the derivative
44 relation---namely, that any two derivatives of the same function must
47 %\begin{convention}% Let [a,b:IR] with [a [<] b] and denote by [I] the
48 interval [[a,b]]. Throughout this chapter, [F, F', G, G'] and [H]
49 will be partial functions with domains respectively [P, P', Q, Q'] and
55 cic:/CoRN/ftc/Derivative/Definitions/a.var
59 cic:/CoRN/ftc/Derivative/Definitions/b.var
63 cic:/CoRN/ftc/Derivative/Definitions/Hab'.var
68 inline procedural "cic:/CoRN/ftc/Derivative/Definitions/Hab.con" "Definitions__" as definition.
70 inline procedural "cic:/CoRN/ftc/Derivative/Definitions/I.con" "Definitions__" as definition.
75 cic:/CoRN/ftc/Derivative/Definitions/F.var
80 inline procedural "cic:/CoRN/ftc/Derivative/Definitions/P.con" "Definitions__" as definition.
84 inline procedural "cic:/CoRN/ftc/Derivative/Derivative_I.con" as definition.
91 Implicit Arguments Derivative_I [a b].
95 Section Basic_Properties
98 (*#* **Basic Properties
102 cic:/CoRN/ftc/Derivative/Basic_Properties/a.var
106 cic:/CoRN/ftc/Derivative/Basic_Properties/b.var
110 cic:/CoRN/ftc/Derivative/Basic_Properties/Hab'.var
115 inline procedural "cic:/CoRN/ftc/Derivative/Basic_Properties/Hab.con" "Basic_Properties__" as definition.
117 inline procedural "cic:/CoRN/ftc/Derivative/Basic_Properties/I.con" "Basic_Properties__" as definition.
122 Like we did for equality, we begin by stating a lemma that makes proofs of derivation easier in practice.
125 inline procedural "cic:/CoRN/ftc/Derivative/Derivative_I_char.con" as lemma.
130 Derivative is a well defined relation; we will make this explicit for both arguments:
134 cic:/CoRN/ftc/Derivative/Basic_Properties/F.var
138 cic:/CoRN/ftc/Derivative/Basic_Properties/G.var
142 cic:/CoRN/ftc/Derivative/Basic_Properties/H.var
147 inline procedural "cic:/CoRN/ftc/Derivative/Basic_Properties/P.con" "Basic_Properties__" as definition.
149 inline procedural "cic:/CoRN/ftc/Derivative/Basic_Properties/Q.con" "Basic_Properties__" as definition.
151 inline procedural "cic:/CoRN/ftc/Derivative/Basic_Properties/R.con" "Basic_Properties__" as definition.
155 inline procedural "cic:/CoRN/ftc/Derivative/Derivative_I_wdl.con" as lemma.
157 inline procedural "cic:/CoRN/ftc/Derivative/Derivative_I_wdr.con" as lemma.
161 inline procedural "cic:/CoRN/ftc/Derivative/Basic_Properties/Derivative_I_unique_lemma.con" "Basic_Properties__" as definition.
166 Derivative is unique.
169 inline procedural "cic:/CoRN/ftc/Derivative/Derivative_I_unique.con" as lemma.
172 Finally, the set where we are considering the relation is included in the domain of both functions.
175 inline procedural "cic:/CoRN/ftc/Derivative/derivative_imp_inc.con" as lemma.
177 inline procedural "cic:/CoRN/ftc/Derivative/derivative_imp_inc'.con" as lemma.
180 Any function that is or has a derivative is continuous.
184 cic:/CoRN/ftc/Derivative/Basic_Properties/Hab''.var
187 inline procedural "cic:/CoRN/ftc/Derivative/deriv_imp_contin'_I.con" as lemma.
189 inline procedural "cic:/CoRN/ftc/Derivative/deriv_imp_contin_I.con" as lemma.
196 If [G] is the derivative of [F] in a given interval, then [G] is also the derivative of [F] in any smaller interval.
199 inline procedural "cic:/CoRN/ftc/Derivative/included_imp_deriv.con" as lemma.