s19aa Method
関数リスト一覧   NagLibrary Namespaceへ  ライブラリイントロダクション  本ヘルプドキュメントのchm形式版

s19aa returns a value for the Kelvin function berx.

Syntax

C#
public static double s19aa(
	double x,
	out int ifail
)
Visual Basic (Declaration)
Public Shared Function s19aa ( _
	x As Double, _
	<OutAttribute> ByRef ifail As Integer _
) As Double
Visual C++
public:
static double s19aa(
	double x, 
	[OutAttribute] int% ifail
)
F#
static member s19aa : 
        x:float * 
        ifail:int byref -> float 

Parameters

x
Type: System..::.Double
On entry: the argument x of the function.
ifail
Type: System..::.Int32 %
On exit: ifail=0 unless the method detects an error (see [Error Indicators and Warnings]).

Return Value

s19aa returns a value for the Kelvin function berx.

Description

s19aa evaluates an approximation to the Kelvin function berx.
Note:  ber-x=berx, so the approximation need only consider x0.0.
The method is based on several Chebyshev expansions:
For 0x5,
berx='r=0arTrt,   with ​ t=2 x5 4-1.
For x>5,
berx= ex/22πx 1+ 1xat cosα+ 1xbtsinα + e-x/22πx 1+ 1xct sinβ+ 1xdtcosβ ,
where α= x2- π8 , β= x2+ π8 ,
and at, bt, ct, and dt are expansions in the variable t= 10x-1.
When x is sufficiently close to zero, the result is set directly to ber0=1.0.
For large x, there is a danger of the result being totally inaccurate, as the error amplification factor grows in an essentially exponential manner; therefore the method must fail.

References

Error Indicators and Warnings

Accuracy

Further Comments

Example

See Also