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AC-arctan(AC/80)*80=1是數(shù)學(xué)問(wèn)題。, q% ]0 X! O& C1 K4 B3 K
子子大俠既然讀過(guò)VB,那么讀VBA代碼就應(yīng)該沒(méi)什么困難,核心是數(shù)值計(jì)算。
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( X' Q% z y z9 N" J定義待求解函數(shù):8 j+ H0 I1 ~. T, n4 o& q7 x3 B
Public Function QesFun(ByVal Var_AC As Double) As Double
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( F& x+ j& ~9 ~0 E QesFun = Var_AC - Atn(Var_AC / 80) * 80 - 1
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End Function
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1. 二分法/ A" \9 r( t6 T" t
1.1 由 Arctan(AC/80)=(AC-1)/80' d* [9 M3 o& k& n5 X
知 -PI()/2<(AC-1)/80< PI()/2
, Q W3 i$ s; a8 ^ 即 1 -80*PI()/2<AC<1+ 80*PI()/21 X: [8 D& |, H5 o8 |* Y r- Q
++++++++++++++++++++++++++++++++++++++
% r* f" j& a: M6 a0 h1.2定義求解函數(shù):
/ _7 a% a" U9 Q( m8 W! lPublic Function SolFunDic(ByVal MaxLim As Double, ByVal MinLim As Double) As Double0 V; c0 I1 x! F0 c: L4 ?. c
% ^ f+ y: f9 K' v9 Q+ \, e* I( ]Dim Res#, VarAdj#
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3 w: O+ V4 v# p9 n$ V! j3 sVarAdj = 10 ^ -6
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4 Z9 {0 @; d/ G' ZIf QesFun(MinLim + VarAdj) < QesFun(MaxLim - VarAdj) Then+ X- _8 K) G' X3 H. g
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Do While (1)
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Res = (MaxLim + MinLim) / 2
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r1 I$ C( f& l/ E A8 U! ]4 W If Abs(QesFun(Res)) <= 10 ^ -12 Then
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- ]5 |- {# ]4 p( z; Q. f0 W, \% s* V SolFunDic = Res: Exit Do1 i0 h" d3 p& m9 ?+ c$ s6 ^
. m" g6 @5 k& z; @4 l ElseIf (QesFun(Res) < 0) Then
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, z# s; b7 A5 P; q MinLim = Res
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Else, }& [7 T2 c# M2 V) q
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MaxLim = Res
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End If: ^) r& }! \/ A
! c1 L9 |) ^ o+ C) M4 ]* n Loop
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4 a4 |7 C; i( z' ^7 \* `Else
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Do While (1)
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Res = (MaxLim + MinLim) / 28 @8 I7 g. ?; S$ _6 [
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If Abs(QesFun(Res)) <= 10 ^ -12 Then
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$ L/ o# @9 u, l6 X6 p SolFunDic = Res: Exit Do
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5 n: M- d) j7 ]% }/ D ElseIf (QesFun(Res) > 0) Then
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7 ]7 M3 [7 f7 e, }! U! l! l/ \ MinLim = Res; A: M& m! {: z$ E3 {3 d
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Else# @: h; ^' x+ m2 V- Y# d4 z
! k# T+ L' x; q1 ?0 q MaxLim = Res
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8 H& V8 F5 B& U9 m8 s o% i+ h End If$ t) v- k4 Y: ?, r% d1 v. U
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Loop% w# p1 k, V5 m& H6 W1 q
4 L( \* k9 K( T4 N5 \End If) x$ q/ K0 [* H$ j! W. e
End Function( J1 M7 r5 d( a1 x. E# r9 \
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/ e1 ^* m' O6 h2. 牛頓法
! g. \ S: m, x: I2.1 由 f(AC)=arctan(AC/80)*80+1-AC' k$ t; S1 Z' p* l7 G+ C
求導(dǎo) f(AC)’=1/(1+(AC/80)^2)-12 [/ f: b4 @, h& A( b
即 AC_1=AC_0- f(AC)/ f(AC)’. t) ^$ E G) _; l/ k- H7 Q/ M
--------------------------------------------------------------' v% R w4 z5 _+ u Z% E
2.2定義迭代函數(shù):7 t1 U5 {& s* z% M. J8 g# u
Public Function QesFunNew(ByVal Var_AC As Double) As Double
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/ G& T" D9 f7 ^" `9 E# M; s( @ QesFunNew = Var_AC - (Atn(Var_AC / 80) * 80 + 1 - Var_AC) / (1 / (1 + (Var_AC / 80) ^ 2) - 1)
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; d; j; ~3 s8 d( B+ ?; _, GEnd Function
7 ` |1 b: g% j# g# W---------------------------------------------------------------
! Q8 l' Q4 ?6 w6 B9 {9 U x: l7 c2.3定義求解函數(shù)
9 K% h, d! t: [Public Function SolFunNew(ByVal IniAC As Double) As Double7 E: c8 k# o' w) a- d9 y
; ~) d3 i2 g5 V$ k! u" k+ m: eDim Res#
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$ X! e9 k2 b7 W7 j) W4 L( bDo While (1)
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Res = QesFunNew(IniAC)' k7 r0 p+ d6 T. f
2 J+ a9 r; W/ N7 D: X If Abs(QesFun(Res)) <= 10 ^ -12 Then* y. Z1 t/ | t, |% z/ k2 J1 ~, C6 E
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SolFunNew = Res: Exit Do
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1 w; w g4 z0 {1 p0 y g! I Else
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IniAC = Res, m, f0 c5 a! n8 H- z
0 b6 M8 K; k6 { End If
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7 A* K2 ?, V* z& k7 ?* LLoop
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這樣做可能有點(diǎn)麻煩,但涉及到循環(huán),迭代時(shí),可自由調(diào)用自定義VBA函數(shù)和工作表函數(shù)(矩陣計(jì)算連桿機(jī)構(gòu)),還可控制輸出表格,便于插圖。計(jì)算冷卻塔時(shí),積分得用辛普遜;解汽水比,得解非線性方程。對(duì)這些問(wèn)題,EXCEL 工作表自身好像很吃力。* E. d5 C+ z) h; Q. o P
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