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MathGroup Archive 2011

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Bad Precision output for SphericaBesselY and BesselY

  • To: mathgroup at smc.vnet.net
  • Subject: [mg123069] Bad Precision output for SphericaBesselY and BesselY
  • From: Antonio Alvaro Ranha Neves <aneves at gmail.com>
  • Date: Tue, 22 Nov 2011 05:36:13 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • Reply-to: comp.soft-sys.math.mathematica at googlegroups.com

Dear users,

Recently I'm working with precision calculations of spherical functions. Example, let,

n = 150
x = SetPrecision[120.3, 100]
BesselY[n + 1/2, x] // Precision
BesselJ[n+ 1/2, x] // Precision


Yields 67.2708 and 96.9297 respectively. The two questions are:
1) Why does BesselY results in a worse than BesselJ?
2) How to redefine, BesselY to automatically output a result with a desired pecision?

Note: Simply using N[expr,90], does not yield a result of expr with 90 precision but maintains the same 67.2708.

Thanks,
Antonio




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