93 lines
2.7 KiB
VB.net
93 lines
2.7 KiB
VB.net
#Region "Microsoft.VisualBasic::fbb2ea48f2dd4d815304d189f668b4b9, Microsoft.VisualBasic.Core\Extensions\Math\Trigonometric\Arctan.vb"
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' Author:
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'
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' asuka (amethyst.asuka@gcmodeller.org)
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' xie (genetics@smrucc.org)
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' xieguigang (xie.guigang@live.com)
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'
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' Copyright (c) 2018 GPL3 Licensed
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'
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'
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' GNU GENERAL PUBLIC LICENSE (GPL3)
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'
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'
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' This program is free software: you can redistribute it and/or modify
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' it under the terms of the GNU General Public License as published by
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' the Free Software Foundation, either version 3 of the License, or
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' (at your option) any later version.
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'
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' This program is distributed in the hope that it will be useful,
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' but WITHOUT ANY WARRANTY; without even the implied warranty of
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' MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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' GNU General Public License for more details.
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'
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' You should have received a copy of the GNU General Public License
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' along with this program. If not, see <http://www.gnu.org/licenses/>.
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' /********************************************************************************/
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' Summaries:
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' Module Trigonometric
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'
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' Function: Atn
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'
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'
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' /********************************************************************************/
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#End Region
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Imports sys = System.Math
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Namespace Math
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Partial Module Trigonometric
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Const HalfPI# = PI / 2
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Const n1# = 1.0R
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Const n05# = 0.5R
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''' <summary>
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''' 通过这个参数来控制计算精度，这个参数值越大，计算精度越高
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''' </summary>
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Public AtanPrecise% = 500
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''' <summary>
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''' Taylor Atan
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''' </summary>
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''' <param name="x"></param>
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''' <returns></returns>
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''' <remarks>Atan测试没有问题</remarks>>
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Public Function Atn(x#) As Double
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If x# = 1.0 Then
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Return PI / 4
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End If
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If sys.Sign(x) = sys.Sign(-1) Then
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Return -Atn(-x)
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End If
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If x > n1 Then
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Return HalfPI - Atn(1 / x)
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End If
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If x > n05 Then
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Return Atn(n1) + Atn((x - n1) / (1 + x))
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Else
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Dim xPow2 As Double = x * x
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Dim n__1 As Integer = AtanPrecise
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Dim y As Double = 1 / (2 * n__1 + 1)
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Dim i As Integer = AtanPrecise
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While i > 0
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y = (1 / (2 * n__1 - 1)) - (xPow2 * y)
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i -= 1
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n__1 -= 1
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End While
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Return x * y
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End If
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End Function
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End Module
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End Namespace
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