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数学专业英语-(a) How to define a mathematical term?
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+ }. ~" y# i2 k$ }# E 数学术语的定义和数学定理的叙述,其基本格式可归纳为似“if…then…”的格式,其他的格式一般地说可视为这一格式的延伸或变形。 Q/ i* O' k0 j+ K3 T, @
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如果一定语短语或定语从句,以界定被定义的词,所得定义表面上看虽不是“If……then……”的句型,而实际上是用“定语部分”代替了“If”句,因此我们可以把“定语部分”写成If句,从而又回到“If……then……”的句型。 ( U0 q% ]2 A; |0 t# @) ^4 [% k, }, @
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7 x5 I7 D' t$ t+ V5 I 至于下面将要叙述的“Let…if…then”,“Let and assume…, If…then…”等句型,其实质也是基本句型“If……then……”的延伸。 ; I6 a+ B+ `3 d* J: y( T+ D; R3 Y6 V+ @
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有时,在定义或定理中,需要附加说明某些成份,我们还可在“if…then…”句中插入如“where…”等的句子,加以延伸(见后面例子)。
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) B/ m# t: { s& |5 I7 X4 z 总之,绝大部分(如果不是全部的话)数学术语的定义和定理的叙述均可采用本附录中各种格式之。 % T; A0 q& E9 }: R
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& I- A( g! Q/ @) |# R Q (a)How to define a mathematical term?
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is defined as
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! ~ i; z4 S& w! _0 o7 G is called . A4 g% W* B/ Z9 h- `
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1. Something something
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The union of A and B is defined as the set of those elements which are in A, in B or in both. * g& ^+ n3 b" I& I; q) _
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The mapping , ad-bc 0, is called a Mobius transformation. & {5 Q7 l" j' h8 }5 S& d
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& L9 b: S5 Z: @! w3 W3 F is defined to be
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is said to be $ x G. C5 ^5 j' Y: V
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! W$ j/ h4 B1 a1 s0 c7 ^6 ?2. Something something(or adjective) ) O6 P& W0 @* F, P H6 J+ I
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" A* p1 G9 q- d7 e0 v The difference A-B is defined to be the set of all elements of A which are not in B. 4 e" X5 [9 {5 e5 I5 E+ `/ c
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A real number that cannot be expressed as the ratio of two integers is said to be an irrational number. " A/ K, K+ H4 ^- k( X u2 o: `7 p, V
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Real numbers which are greater than zero are said to be positive.
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define
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2 R% r L5 z' l& e5 r0 [7 A3. We something to be something. + J: }3 |0 u5 M8 [' m1 I9 a+ s
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& v& m. a+ b; b# V7 e( v* G5 P P We define the intersection of A and B to be the set of those elements common to both A and B.
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We call real numbers that are less than zero (to be) negative numbers.
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8 z `# d3 R T& d. p% N7 @/ s 4. 如果在定义某一术语之前,需要事先交代某些东西(前提),可用如下形式: # d1 ?; h) _( S0 L) H
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is called 7 D% R& Y, T8 A, B8 [1 {2 h/ m- u
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is said to be
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is defined as
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is defined to be 5 \+ a/ [3 g5 G0 ^: `2 W# [
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Let…, then…
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3 e/ B/ I3 @- A, ~% g# E Let x=( ) be an n-tuple of real numbers. Then the set of all such n-tuples is defined as the Euclidean n-space R.
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Let d(x,y) denote the distance between two points x and y of a set A. Then the number / A# @/ a& `% _5 L. ]0 g% g; s
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D=
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5.如果被定义术语,需要满足某些条件,则可用如下形式: , S# ?: a& X3 @0 Q+ ^
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is said to be : f. e/ S- ^5 X4 J. w! P* ]
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is defined to be
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7 j! n5 S: N- k- s- {# k9 q2 I If…, then… 2 V& o$ O V; y+ C J
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If the number of rows of a matrix A equals the number of its columns, then A is called a square matrix.
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7 N2 i1 Z, w1 ~# E: B If a function f is differentiable at every point of a domain D, then it is said to be analytic in D.
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( J0 L4 N: I! S. S 6.如果需要说明被定义术语应在什么前提下,满足什么条件,则可用下面形式: - V3 D; [1 A, o& C F
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is called % E/ u/ n7 ~$ i# d9 D2 V3 l" I
is said to be | % Y* A) K7 f A' `7 y) O
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% A6 | j2 r; l% R$ Y/ I+ Q( v/ K p8 ^Let
- F0 T+ p$ f! hSuppose | …. If…then… …
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; u- S: f7 m- m9 _) z& ?( j6 |5 l Let f(z) be an analytic function defined on a domain D (前提条件). If for every pair or points , and in D with , we have f( ) f( ) (直接条件),then f(z) is called a schlicht function or is said to be schlicht in D.
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