Public Function BesselK( _ ByVal vX As Variant _ , ByVal vFNU As Variant _ ) As Variant
BesselK(.5, 0) = 0.924419071227663 BesselK(.5, 1) = 1.6564411200033 BesselK(.5, 1.5) = 3.22514281049976 BesselK(.5, 2) = 7.55018355124087 BesselK(.5, 0) = BesselK0(.5) BesselK(.5, 1) = BesselK1(.5)See also:
BesselK0 Function BesselK0E Function BesselK1 Function BesselK1E Function BesselKE Function BesselI Function BesselJ Function BesselY Function DBESK SubroutinevX: Function returns Null if vX is Null or cannot be fixed up to a Double precision floating point number.
BesselK implements forward recursion on the three term recursion relation for a one member sequence of non-negative order Bessel functions K/sub(FNU)/(X), for real X > 0 and non-negative orders FNU. If FNU < NULIM, orders FNU and FNU+1 are obtained from DBSKNU to start the recursion. If FNU >= NULIM, the uniform asymptotic expansion is used for orders FNU and FNU+1 to start the recursion. NULIM is 35 or 70 depending on whether N=1 or N >= 2. Under and overflow tests are made on the leading term of the asymptotic expansion before any extensive computation is done.
The maximum number of significant digits obtainable is the smaller of 14 and the number of digits carried in double precision arithmetic.
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