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#2
lianyicq2015-05-18 08:48
到底是求r还是f(r)?
是想用试探法来求？但是不知道函数值f(r)无法试探。阿尔法也未知？r有没有取值范围。 ... 只想到笨办法  程序代码：Function r(R1 As Single, R2 As Single, R3 As Single, a As Single, StepJ As Single, ErrJ As Single) As Single 看看能不能达到目的Dim temp As Single For j = MinJ To MaxJ Step StepJ temp = 2 * j * (R1 - R2) + R1 ^ 2 - R2 ^ 2 + (R1 + R2) ^ 2 - 2 * (R1 + R2) * Cos(a * (R1 + j * (R1 - R3) / (R1 + R3))) - 2 * (R1 + R2) * Sin(a * 2 * Sqr(R1 * R3) * Sqr(j ^ 2 + j * (R1 + R3)) / (R1 + R3)) If Abs(temp) < ErrJ Then r = j Exit For End If Next End Function ... EXCEL自带用迭代法求解超越方程的功能，用到了数据工具里的假设分析，可以试试。 如果用代码写迭代算法 只有本站会员才能查看附件，请 登录 [attach]80337[/attach] 代码按笨办法的方式写。 写了一个小例子计算y=cosx-x的解 程序代码：'Example for y=cos-x Option Explicit Private Sub Command1_Click() Dim Y As Single, DY As Single Dim ERR As Single Dim times As Long Dim XK As Single times = 0 Y = 1 'Ensure Y>ERR in the first time ERR = 0.0001 XK = Val(Text3.Text) While (Abs(Y) > ERR) If times <> 0 Then XK = XK - Y / DY Y = Cos(XK) - XK DY = -Sin(XK) - 1 times = times + 1 Wend Form1.Caption = Y & " " & times & " " & XK End Sub [ 本帖最后由 lianyicq 于 2015-5-19 09:28 编辑 ] |
For j = 2 To 1000
x = r1 * (1 - 0.001 * j)
y = 2 * x * (r1 - r2) + r1 * r1 - r2 * r2 + (r1 + r2) * (r1 + r2) - 2 * (r1 + r2) * Cos(a) * (r1 + x * (r1 - r3) / (r1 + r3)) - 2 * (r1 + r2) * Sin(a) * 2 / (r1 + r3) * Sqr(r1 * r3) * Sqr(x ^ 2 + x * (r1 + r3))
If y < 0 Then Next j
x = r1 * (1 - 0.001 * j)
y = 2 * x * (r1 - r2) + r1 * r1 - r2 * r2 + (r1 + r2) * (r1 + r2) - 2 * (r1 + r2) * Cos(a) * (r1 + x * (r1 - r3) / (r1 + r3)) - 2 * (r1 + r2) * Sin(a) * 2 / (r1 + r3) * Sqr(r1 * r3) * Sqr(x ^ 2 + x * (r1 + r3))
If y > 0 Then Exit For
End If
End If
End Function
主要想求求解以下方程：
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R1,R2,R3,a 都是已知量，就是求r.
请哪位高手帮忙，万分感谢。
