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Bad Precision output for SphericaBesselY and BesselY

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  • Subject: [mg123069] Bad Precision output for SphericaBesselY and BesselY
  • From: Antonio Alvaro Ranha Neves <aneves at>
  • Date: Tue, 22 Nov 2011 05:36:13 -0500 (EST)
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  • Reply-to: comp.soft-sys.math.mathematica at

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.


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